Activision has signed a new deal with Valve Software that will see four of its titles being made available through the Steam digital distribution service.
The games, which will be released over Steam by the end of October, are Call of Duty, COD 2, COD United Offensive and Gun.
"Our agreement with Steam enhances our current online distribution model by allowing us to bring our games to the broadest possible audience," said Activision exec Dave Anderson.
"As broadband penetration continues to grow worldwide, offering our titles digitally to the millions of gamers connected through Steam makes sense to us."
According to Valve, Steam now has more than 10 million registered users. Recently added games include Defcon, Advent Rising and Psychonauts, all of which are priced at under USD 20.