Summary.-Images of pleasant scenes usually produce increased activity over the zygomaticus major muscie, as measured by electromyography (EMG), while less activity is elicited by unpleasant images. However, increases in zygomaticus major EMG activity while viewing unpleasant images have occasionally been reported in the literature on affective facial expression (i.e., "grimacing"). To examine the possibility that individual differences in emotion regulation might be responsible for this inconsistently observed phenomenon, the habitual emotion regulation tendencies of 63 participants (32 women) were assessed and categorized according to their regulatory tendencies. Participants viewed emotionally salient images while zygomaticus major EMG activity was recorded. Participants also provided self-report ratings of their experienced emotional valence and arousal while viewing the pictures. Despite demonstrating intact affective ratings, the "grimacing" pattern of zygomaticus major activity was observed in those who were less likely to use the cognitive reappraisal strategy to regulate their emotions.