Oklahoma Gin is a variation on Gin Rummy, in which the first upcard determines the maximum number of points with which a player may knock in that deal. Face cards count as 10, aces as 1, and number cards as their face value. For example, if the upcard was a 5, the player must have five points or less in their deadwood before they can knock.
Many players adopt the rule that if the upcard is an ace, a player may only go out with a gin hand.
In addition, the "Spades Double" rule may be used, in which case a spade as the upcard causes all points in that hand to count double.
The target score for winning Oklahoma Gin is generally set at 150 rather than 100.