To assess objectively the effects of emotional stimuli on the severity of tics and to determine if such effects were mediated by the autonomic nervous system, we carried out videotape ratings of tics and electrophysiological monitoring of heart beat and respiration on 4 children with Tourette's syndrome while they were watching a movie known to elicit emotional responses relevant to normal childhood events. Measured tic severity was highest during periods associated with anticipation, resolution of emotional changes, and lower concentration, lowest during periods of anger and happiness, and intermediate during periods of sadness and fear. Tic severity did not correlate with heart or respiratory rate. Thus, tics seem influenced differentially by various emotional states, but this effect does not seem to be autonomically mediated.