Westchester County has gained ground as a headquarters site for Big Business.

The latest rankings of the Fortune 500 released Sunday showed that eight Westchester companies made the list of the nation’s largest companies, up from six companies a year ago. The increase reflected the strong sales growth at MasterCard Inc., the Purchase-based credit card giant, and Universal American Corp., the Rye Brook-based health insurer, that made them new members of the Fortune 500.

Nationally, Exxon Mobil Corp. topped Wal-Mart Stores Inc. as the largest company on the list.

Fortune magazine will feature the list in its May 4th issue that is expected to hit newsstands on April 27.

Westchester companies on the list included:
•IBM Corp., the Armonk-based technology company with revenues of $103.6 billion. IBM, which ranked No. 14 on the Fortune 500 this year, up from No. 15 last year, has held up well in the recession and consistently announced new technology contracts around the world.
•PepsiCo Inc., the Purchase-based beverage and snack food giant with revenues of $43.3 billion. PepsiCo’s ranking rose to No. 52 from No. 59, despite softer beverage sales in a slow economy.
•Pepsi Bottling Group, the Somers-based beverage distributor with revenues of $13.8 billion, ranked No. 189, nearly unchanged from No. 190 a year earlier. The company has used acquisitions to become the world’s largest distributor of Pepsi products.
•ITT Corp., the White Plains-based industrial company with revenues of $11.7 billion. ITT’s ranking rose to No. 229 from No. 285 a year ago as it benefited from diversified products that range from night-vision goggles to water treatment systems.
•Starwood Hotels & Resorts Worldwide Inc., the White Plains-based operator of the Sheraton and Westin chains with revenues of $5.9 billion. Starwood, which has battled weaker hotel occupancy in a slow economy, slipped to No. 417 from No. 396 a year ago.
•Jarden Corp., the Rye-based consumer products maker with revenues of $5.4 billion, rose to No. 442 from No. 492. Jarden may be less exposed to the slowdown because it generally sells hundreds of less-expensive items such as Ball canning jars, Diamond matches, toothpicks and straws that are popular with budget-minded consumers.
•MasterCard, with revenues of $4.99 billion, has benefited as consumers shifted more purchases to debit and credit cards from cash and check. MasterCard rose to No. 474 from No. 548 in the Fortune rankings.
•Universal American, with revenues of $4.7 billion, said fourth-quarter profits more than doubled as the health insurer benefited from enrollment gains in its Medicare health insurance plans and expansion in new markets. The company’s ranking rose to No. 494 from No. 669.