Increases in penile circumference of 10 incarcerated rapists and 10 male graduate students were measured during verbal descriptions of mutually consenting sex, rape, and violent nonsexual assault. Mutually consenting sex evoked sexual arousal in both groups. Rape evoked comparable arousal in rapists but significantly less arousal in nonrapists. Assault evoked significantly less arousal in nonrapists and tended to evoke less arousal in rapists. However, the rapists did not exhibit greater sexual arousal to forced or violent sex compared with consenting sex, either as a group or as individuals. It is not necessarily true that forced or violent sex evoked rapists' arousal but perhaps that force or violence failed to inhibit their arousal. In conclusion, the results of previous studies were confirmed, in that differential sexual arousal evoked by different descriptions of sexual behavior discriminated between groups of subjects when group membership was defined by rapist and nonrapist sexual behavior. Therefore, deviant sexual arousal in rapists can be differentiated, whether the control group is composed of normal subjects or nonrapist sexual deviates. However, in contrast to previous research, no necessary connection was established between force, violence and nonconsent of the female and sexual arousal of the rapist. One table, one figure, and 20 references are provided.