Westlake Chemical Corporation

Credit Suisse Chemical Conference

September 18, 2008

2

SAFE HARBOR LANGUAGE

This presentation may include forward-looking statements, as defined in the Private Securities Litigation Reform Act of 1995, reflecting management’s current analysis and expectations, based on reasonable assumptions. Results could differ materially depending on such factors as business climate, business performance, economic and competitive uncertainties, ability to execute work process redesign and reduce costs, failure to complete transactions or to achieve benefit from transactions, higher manufacturing costs, change in strategies, reduced level of customer orders, risks in developing new products and technologies, adverse legal and regulatory developments including increases in the number or financial exposures of claims, lawsuits, settlements or judgments, or the inability to eliminate or reduce such financial exposures by collecting indemnity payments from insurers, environmental and safety regulations and clean-up costs, foreign exchange rates, and adverse changes in economic and political climates around the world. Accordingly, there can be no assurance that the Company will meet future results, performance or achievements expressed or implied by such forward-looking statements. As appropriate, additional factors are contained in reports filed with the Securities and Exchange Commission. This paragraph is included to provide safe harbor for forward-looking statements, which are generally not required to be publicly revised as circumstances change.

Investor Relations Contact

Steven BenderSr. Vice President, Chief Financial Officer

& Treasurer

Westlake Chemical Corporation2801 Post Oak Boulevard, Suite 600

Houston, Texas 77056713-960-9111

www.westlake.com

3

AGENDA

Who We Are

Westlake’s Proven Track Record

Outperforming Peers over the Cycle

Financially Disciplined

Investment Conclusion

4

$ 3.7 Billion Integrated Polymers Materials Company

$ 110 millionNet Income

$ 280 millionEBITDA (1)

$ 3.7 billion Sales

MISSIONprofitable growth …in businesses we understand…globally in areas we can gain an edge…in a disciplined and opportunistic manner

Westlake Chemical Corporation(LTM 2nd Qtr 2008)

(1) Non-GAAP financial measure

% of Total

Sales

30%70%

$ 1.1 billion $ 2.6 billion

VinylsOlefins

5

0

2,000

4,000

6,000

8,000

10,000

12,000

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

$0

$500

$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

Capacity(mm lbs)

Revenues

VinylsOlefins

Revenue($ mm)

VALUE CREATION TRACK RECORD –HIGHER GROWTH vs PEERS OVER TWO DECADES

Committed to “Profitable Growth”… not just one without the other

3.2%6.1%Peer A

16.0%17.0%WLK

5.1%6.4%Peer C

4.2%6.0%Peer B

CAGRCapacity

CAGRRevenue

1989 - 2007

Growth

* Note: Estimate from 1989 - 1995

A- NCX; B-GGC; C-Dow

6

AGENDA

Who We Are

Westlake’s Proven Track Record

Outperforming Peers over the Cycle

Financially Disciplined

Investment Conclusion

Favorable Product Mix

Higher Operating Rates

High level of Integration

7

HIGHER OPERATING RATES VS PEERS,PARTICULARLY IN TROUGH YEARS

Ethylene Operating Rates(1) Westlake Advantage over Industry Peers

Higher operating rates, particularly in trough years

Operating culture; execution; integration; newer assets

70

80

90

100

2000 2001 2002 2003 2004 2005 2006 2007

%,

oper

atin

g ra

te

Industry Westlake

4.3%Trough Years, avg.(2001- 2003)

3.2%8-year, avg.

(2000 – 2007)

Operating Rate Advantage vs. Peers

Source: CMAI and Westlake(1) Includes the impact of Hurricane Katrina and Rita in 2005

8

HIGHER OPERATING RATES VS PEERS, PARTICULARLY IN TROUGH YEARS

70

80

90

100

2000 2001 2002 2003 2004 2005 2006 2007

%, o

f ope

ratin

g ra

te

Industry Westlake

Higher WLK operating rates, particularly in trough years

Operating culture, execution, integration

Westlake Advantage over Industry Peers

9.0%Trough Years, avg.(2001- 2003)

4.9%8-year, avg.(2000 – 2007)

Operating RateAdvantage vs. Peers

PVC Operating Rates

Source: CMAI and Westlake

9

SUPERIOR AGE AND COMPETITIVENESS OF OUR ETHYLENE PLANTS

North American Ethylene Plants - Site Age and Capacity

0

5

10

15

20

25

30

35

40

45

50

100 1,000 10,000

Aver

age

Age

(yrs

)

Capacity (mm lbs)

Westlake LC

2000

Small but New

Small and Old

Large and New - Desired!

Large but Old

(Most N. Amer. Crackers)

Source: CMAI

Westlake is well positioned with modern and up to date ethylene plantsMany North American plants of competitors were built pre-1980

10

OLEFINS INTEGRATIONCAPTIVE ETHYLENE PRODUCTION

Merchant, 10%

Polyethylene, 53%1.5 billion lbs

Ethylene2.85 billion lbs

Styrene, 5%0.5 billion lbs

VCM, 32%1.9 billion lbs

Polyethylene, 70%2.5 billion lbs

Ethylene Styrene, 4%2.95 billion lbs 0.5 billion lbs

VCM, 26%1.9 billion lbs

PurchasedEthylene, 17%

Before Longview Acquisition: Long Ethylene

Current: Full Utilization of Ethylene

90% CAPTIVE 90% CAPTIVE PRODUCTIONPRODUCTION

100% CAPTIVE 100% CAPTIVE PRODUCTIONPRODUCTION

Improved level of integration

Positioned for the cycle; can curtail ethylene purchases yet run

Westlake plants at high rates

Opportunity to debottleneck in the future

Enhanced margin stability; higher profits

1111

WESTLAKE’S FAVORABLE PRODUCT MIX in POLYETHYLENE vs. PEERS

Westlake’s PE Business Is Favorably Weighted to LDPE vs. North American Peers

0% 20% 40% 60% 80% 100%

Among the highest LDPE product mix percentage in U.S. and Canada

Westlake

Koch Industries

LyondellBasell

Dow

ExxonMobil

ChevronPhillips

NOVA

Source: Chemical Data, Inc.

1212

0.0

1.0

2.0

3.0

4.0

5.0

2000 - 2007 2001 - 2003 Trough Years

cent

s/ lb

s

3.7 ¢

2.8 ¢

4.1 ¢

3.3 ¢

LDPE More Profitable, Particularly In Trough Years

Befo

re

LLDPE, 29%

LDPE, 26%

HDPE, 45%

Total Capacity: 171 billion poundsSource: CMAI

2007 Global Industry Demand (% share)

Westlake Capacity (% share)

LLDPE, 33%

HDPE, 5%

LDPE, 62%

Total Capacity: 2.5 billion pounds

LDPE

vs.

LLD

PE

LDPE

vs.

HD

PE

LDPE

vs.

LLD

PE

LDPE

vs.

HD

PE

Average Margin Advantage of LDPE vs. other PE Grades

WESTLAKE’S FAVORABLE POLYETHYLENE PRODUCT MIX vs. PEERS

13

HIGH LEVEL OF INTEGRATION IN VINYLS SEGMENT

Polyvinyl Chloride

(PVC)

Caustic Soda

Fabricated

Products

PVC

VCM

PVC Fabricated Products

Vinyl Chloride Monomer

(VCM)

Ethylene Dichloride

(EDC)

CausticSoda

Chlorine

Ethylene

Vinyls Segment

PurchasedChlorine

Merchant Sales

Chlor-Alkali

Expansionunderway

Expansionunderway

Expansionunderway

14

VINYLS INVESTMENT DELIVERS INTEGRATION BETTER THAN PEERS

Westlake

Fab. Products

PVCVCMChlorineEthylene

PVC Pipe#1 or #2 in areas served 985 mm lbs. of annual capacityWestlake focuses on large diameter pipe which has better marginsWestlake capacity is 80% non-residentialPVC pipe is protected from imports due to transportation barriers

Fence, Deck and Railing# 2 producer in North America65mm lbs. of annual capacity

Doors and Window Profiles47mm lbs. of annual capacity

Chlorine and PVC expansions complete Vinyls chemical integration

15

STRONG MARKET SHARE IN PIPE

North American Pipe Corporation

Locations

Vinyl Pipe Plant Locations

Vinyls Chemical Sites: Calvert City, KY; Geismar, LA

16

VINYLS CHINESE FOOTPRINT, UNLIKE MOST PEERS

Suzhou Huasu Plastics Company markets PVC resin and film products to both domestic and export markets, while exporting theWindow profiles to North American marketsEstablished 1992, J.V. with Westlake and Ineos. Westlake has approximately a 60% share in the Joint Venture Located in Suzhou, Jiangsu Province, China - Operations include:

300 million lbs PVC resin plant145 million lbs calendering facility22 million lbs window profiles

17

AGENDA

Feedstock Flexibility

Gas Based Ethylene

Improved Integration

Polyethylene Well-Positioned

Who We Are

Westlake’s Proven Track Record

Outperforming Peers over the Cycle

Financially Disciplined

Investment Conclusion

18

0%

1%

2%

3%

4%

5%

2007 2008 2009 2010 2011 2012

Incr

emen

tal C

hang

e/To

tal C

apac

ity (%

)LDPE LLDPE HDPE

INDUSTRY GLOBAL POLYETHYLENE ADDITIONS FOCUSED ON LLPDE AND HDPE, NOT ON LDPE

However, Westlake is focused on LDPE, a product for which:

- Capacity in the U.S. is not being expanded- North American supply and demand is balanced- New additions intended to primarily serve Asian & European markets

Source: CMAI

19

BENEFITS OF AUTOCLAVE LDPE vs. TUBULAR LDPE

Autoclave Advantage:

With no new autoclave capacity coming online and an aging reactor base, supply/ demand balance for autoclave will grow tighter.Westlake’s autoclave reactors are larger and newest in North America, providing strong margins for many years.

Autoclave LDPE (WLK Focus) Tubular LDPE

Market Focus: More Specialty More Commodity

Suitability for Niches: High Much Less

• Product Mix Broad (desirable) Narrow• Product to Product

Transition: Efficient Costly

Competitive Dynamics:

•Global Capacity Additions None Moderate•Geographic Focus for

New Additions: Not Applicable Asian & European Markets

2020

WESTLAKE FOCUSES ON MORE ON DESIREABLE “AUTOCLAVE” LDPE REACTORS

20%80%

Tubular Autoclave, Specialty & Epolene

Westlake Key Product Lines• Autoclave LDPE and our Specialty Polymers

Key Markets• Food Packaging, Extrusion Coating, Protective Packaging, Shrink Wrap

Westlake LDPE Mix

54%

46%

Tubular Autoclave

World LDPE Mix

Source: CMAI, 2007

2121

LAKE CHARLES FEEDSTOCK FLEXIBILITY TO HELP OPTIMIZE MARGINS

Westlake has enhanced flexibility to switch ethylene feedstocks, since no one feedstock is always advantaged.

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

1992

1994

1996

1998

2000

2002

2004

2006

2008

E

2010

E20

12E

cent

s/lb

Naphtha cash margin Ethane cash margin

Ethylene Margin Trend for Light and Heavy Feed Crackers the U.S.

Source: CMAI

Forecast

22

LAKE CHARLES FEEDSTOCK FLEXIBILITY RANGE

Liquid-Flexible Lake Charles Feedslate Capability (% volume)

2008E U.S. Feedslate(% volume)

No one feedstock is always advantaged

Feedstock Flex Project completed in 2007

Feed-Flex improves cycle average margins and reduces earnings volatility

Benefits also include:Energy cost reduction

100 MM lbs capacity increase

Butane1%Propane

14%

Ethane85%

Light Naphtha

21%

Propane5%

Ethane74%

Naphtha25%

Propane22%

Butane5%

Gas oil6%

Ethane42%

Source: CMAI Forecast

Gas-Flexible Lake Charles Feedslate Capability (% volume)

When Gas Advantaged vs. Oil Oil Advantaged vs. Gas

23

7,000

8,000

9,000

10,000

11,000

12,000

13,000

Capacity(mm lbs)

SUPERIOR PROFITABILITY AND GROWTH OVER THE CYCLE

2002 2004 2006 2008/09

Volume Growth and Improved IntegrationReduced per pound Energy Consumption Asset Enhancement

Chlor-Alkali Expansion Geismar Acquisition

Bristol Pipe Acquisition

Eastman PE Acquisition Feed Flex Project

Chlor-AlkaliPVC ResinPVC Pipe Expansions

EBITDA Growth over the Cycle

Olefins Expansion

Vinyls Expansion

Capacity prior to Expansion

Chlor-Alkali Expansion

2011

24

AGENDA

Strong Balance Sheet

Disciplined Investment Culture

Superior EBITDA Margins

Who We Are

Westlake’s Proven Track Record

Outperforming Peers over the Cycle

Financially Disciplined

Investment Conclusion

25

VALUE CREATION TRACK RECORD -SUPERIOR MARGIN AND ROCE vs. PEERS OVER CYCLE

(1) Adjusted EBITDA is EBITDA adjusted for restructuring charges and outages (WLK)(2) Return on capital employed (ROCE) is defined as operating income (adjusted for restructuring charges) divided by average capital employed.

Peers include: DOW,GGC, NCX

Return on Capital Employed (ROCE)(2)

Range from FY 2003 to FY 2007

0%

10%

20%

30%

40%

WLK Peers Avg

29%

6%

16%

4%

Adjusted EBITDA Margin (1)

0%

5%

10%

15%

20%

2003 - 2007 2001-2003 Trough Years

Westlake Peers

26

SUPERIOR BALANCE SHEET

1.4x

2.2x

1.2x

40.2x

0.0x

2.0x

4.0x

DOW WLK NCX GGC

Debt to Capitalization 29%Net Debt To Capitalization 22%

Actual Capitalization ($ millions) June 30, 2008

Net Debt / EBITDA – LTM 2008 Q2

Long-term debt, incl. current portion 6.625% senior notes due 2016 249 6.75% senior notes due 2032 250 Other debt 50 Total Debt 549

Less: Cash 22 Restricted Cash 146

Total Net Debt 381

Stockholders’ equity 1,334

Total capitalization 1,883

27

CAPITAL SPENDING: DISCIPLINED INVESTMENT CULTURE

$0

$50

$100

$150

$200

$250

$300

$350

$400

$450

'95 '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07 '08E

0%

10%

20%

30%

40%

50%

A c qu is it ion s

D is c r e t io n a r y

M a in t e n a n c e

$121

$262

$307

$79 $77

$44

$86 $86

$45

$216

$29

$135

153.8%8.3%Subtotal

103.0%5.6%Discretionary

50.8%2.7%Maintenance

% of Depreciation% of Sales’98~’07 Average

Total CAPEX as % of Sales

CAPE

X (

$ m

illio

n)CAPEX as %

of Sales

$175-200

$391

2828

INVESTMENT CONCLUSIONS

TRACK RECORD OF OUT-PERFORMING PEERSFocused, best-in-class plastics producerDisciplined operating philosophy, with matching track record

COMPETATIVE ADVANTAGES ARE GETTING STRONGERIntegration of assetsFeedstocks; Geography

WESTLAKE SPECIFIC INITIATIVES: AN ONGOING FEATUREAcquisitions, debottlenecks, advantaged “greenfield” plantsA long history of investing prudently

CULTURE OF CREATING VALUE, WHILE RETAINING FINANCIAL FLEXIBILITY TO FUND OUR GROWTH STRATEGY

Strong financial disciplineFinancial Flexibility

APPENDIX

31

APPENDIX

LTM2003 2004 2005 2006 2007 Q2 2008

Adjusted EBITDA 160,728 326,878 450,932 411,183 280,893 279,953

Debt Retirement Cost (11,343) (15,791) (646) (25,853) - -

EBITDA 149,385 311,087 450,286 385,330 280,893 279,953

Less:

Income Tax (provision) benefit (8,747) (69,940) (118,511) (87,990) (44,228) (35,801)

Interest expense (38,589) (39,350) (23,717) (16,519) (18,422) (28,149)

Depreciation & Amortization (87,293) (81,075) (81,241) (86,262) (103,514) (106,176)

Net Income 14,756 120,722 226,817 194,559 114,729 109,827

Changes in operating assets and liabilities 56,219 (35,129) 45,885 28,773 (57,849) (89,843)

Deferred income taxes 7,112 65,188 45,745 13,852 5,286 (43)

Cash flow from operating activities 78,087 150,781 318,447 237,184 62,166 19,941

Reconciliation of EBITDA to Net Income (Loss) and to Cash Flow from Operating Activities (in $ Thousands)