Zynga's online title Mafia Wars is being played by over four million users every day, claims the company.
The game is playable over Facebook, Tagged, Yahoo and Myspace, and has most recently been ported to the iPhone as a free App.
"Mafia Wars is on its way to becoming a cult classic," commented Bill Mooney, executive producer of MMO Studios at Zynga.
According to Zynga, use of the game has doubled in the past three months. Zynga has 12 million daily users across its games, which include Vampires Bloodlust, Pirates and FarmVille.
To celebrate the milestone and one year of live play, Zynga is now offering a new destination in-game to users, along with new items and upgrades.
"We have the most dedicated and loyal players who have made the game a hit and we want to thank them by extending the game in a dynamic destination that makes the game unique and challenging," added Mooney.