Participants were chosen from a national sample of 3,187 college women. The validity of the Sexual Experiences Survey (SES) is evidenced by a comparison of the victims' responses on the SES with their responses to an interviewer. The Pearson correlation between a woman's level of victimization based on her response to an interview and her responses to the SES was .73. Only 3 percent of women, whose responses on the SES indicated they were rape victims, changed their responses during the interview. The dependent variables were obtained from the responses of the victims and were grouped into the following six categories: victim perceptions, offender aggression, victim/offender acquaintance, victim resistance, impact, and symptoms. Group sexual assaults, compared to individual sexual assaults, were characterized by greater violence, involved greater resistance from the victims, were perpetrated by strangers or relatives, usually involved a rape, and were less likely to involve multiple episodes by the same offenders. The victims of group sexual assaults were more likely to seek police and crisis service, to have contemplated suicide, and to have sought therapy post-assault than the individual sexual assault victims. Despite these differences, the two groups were similar in the amount of drinking and drug use during the assault and their scores on standardized measures of psychological symptoms. 3 tables, 1 note, and 18 references (Author abstract modified)