The first titles to appear on Steam from 2K include Civilization III and Civilization IV from Firaxis, Sid Meier's Pirates! and Shattered Union. These will begin to appear on Steam later this week.

"We are excited to add Valve to our roster of partners in the digital distribution area," said Paul Crockett, an executive in 2K's strategic sales and licensing department. "Being included in their vast network will assist us in expanding the reach of our products to a much larger audience."

2K is the latest in a string of publishers to jump aboard Steam, joining recent Steam additions such as Call of Duty 2 from Activision and Psychonauts from Majestic. A statement issued by Valve states that Steam currently has around 10 million customers for both core products and casual games, so it's no wonder that publishers are beginning to support the service.