Emotion regulation plays a central role in mental health and illness, but little is known about even the most basic forms of emotion regulation. To examine the acute effects of inhibiting negative and positive emotion, we asked 180 female participants to watch sad, neutral, and amusing films under 1 of 2 conditions. Suppression participants (N = 90) inhibited their expressive behavior while watching the films; no suppression participants (N = 90) simply watched the films. Suppression diminished expressive behavior in all 3 films and decreased amusement self-reports in sad and amusing films. Physiologically, suppression had no effect in the neutral film, but clear effects in both negative and positive emotional films, including increased sympathetic activation of the cardiovascular system. On the basis of these findings, we suggest several ways emotional inhibition may influence psychological functioning.