The “gambler's fallacy” is the false belief that a random event is less likely to occur if the event has occurred recently. Such beliefs are false if the onset of events is in fact independent of previous events. We study gender differences in the gambler's fallacy using data from the Danish state lottery. Our data set is unique in that we track individual players over time which allows us to investigate how men and women react with their number picking to outcomes of recent lotto drawings. We find evidence of gambler's fallacy for men but not for women. On average, men are about 1% less likely to bet on numbers drawn in the previous week than on numbers not drawn. Women do not react significantly to the previous week's drawing outcome.