All of the analyses found that sexual aggressors and sexual murderers had backgrounds, personal characteristics, and criminal careers that had more similarities than differences. The significant difference between these two types of sexual offenders was the cumulative degree of their developmental disturbance. There was no significant difference in the exposure of sexual murderers and sexual aggressors to deviant/antisocial models of attitudes and behaviors. More than half of the subjects in both groups of sexual offenders had been exposed to abusive alcohol consumption and psychological violence prior to age 18, and approximately half of the subjects in both groups had witnessed physical violence prior to that age. A high proportion of both groups of offenders had drug and alcohol problems, with sexual murderers beginning to consume alcohol and drugs regularly at significantly younger ages than the sexual aggressors. Sexual murderers reported having had significantly more inappropriate childhood and adolescent behaviors than did sexual aggressors. Sexual murderers also had more severe deficits in education and more frequent and severe atypical sexual behaviors and deviant sexual fantasies. Eighty-five percent of sexual aggressors and 92 percent of sexual murderers had criminal records, with no significant difference in the prevalence of convictions for sexual crimes between the two groups. Information on developmental factors came from interviews with 101 sexual aggressors and 40 sexual murderers. Information on adult criminal careers was obtained from the Royal Canadian Mounted Police's Fingerprint System files. 4 tables, 1 figure, and 2 case studies