Facial expression and emotional stimuli were varied orthogonally in a 3 x 4 factorial design in order to test whether facial expression is necessary or sufficient to influence emotional experience. Subjects watched a film eliciting fear, sadness, or no emotion, while holding their facial muscles in the position characteristic of fear or sadness, or in an effortful but nonemotional grimace; those in a fourth group received no facial instructions. The subjects believed that the study concerned subliminal perception and that the facial positions were necessary to prevent physiological recording artifacts. The films had powerful effects on reported emotions, the facial expressions none. Correlations between facial expression and reported emotion were zero. Sad and fearful subjects showed distinctive patterns of physiological arousal. Facial expression also tended to affect physiological responses in a manner consistent with an effort hypothesis.