Impaired capacity for physiological habituation may contribute to the persistence of PTSD. Habituation of autonomic responses to auditory tones was examined in 43 women in three groups: 14 adult female rape survivors with chronic PTSD, 11 without PTSD, and a comparison group of 18 who had not been raped. There were no significant differences among the groups in baseline cardiac or electrodermal activity. The PTSD group showed significantly slower electrodermal habituation, as measured by trials to extinction and percentage of nonhabituators, than did the comparison groups. The present study found slower habituation of electrodermal responses for PTSD rape victims to neutral stimuli than for non-PTSD victims and nonvictims.