The effects of gender stereotype activation by priming on performance in a spatial task were investigated among a mixed adult sample (including students) of 161 men and women (mean age=31.90) from Austria (Europe). They were assigned to one of four experimental groups according to gender and stereotype activation condition. After a male or female gender stereotype activating task, participants worked on a test assessing mental rotation (three-dimensional cube test, Gittler 1990). A significant main effect of priming on the performance in the mental rotation task emerged. Cohen's d showed a pronounced gender difference emerging only in the female priming condition (d=.59), whereas it disappeared in the male priming condition (d=.01).