The data for this study on sibling incest perpetrators was compiled from retrospective chart reviews of clinical intake material. Sources of information included demographic data, perpetrator reports, parent reports, victim reports, police reports, child protective services reports, school records, psychosocial evaluations, mental status examinations, and child behavior checklists. The sample of sibling incest offenders consisted of 12 males who were referred for evaluation and treatment to a hospital-based, outpatient psychiatric clinic. Eighty-three percent of the subjects had parents married to one another and living at home. In contrast to high percentages of prior sexual victimization of the offenders that has been found for juvenile and adolescent sexual offenders in general and sibling incest offender particularly, only one offender in this sample had such a history; however, the finding of high percentages of sexual victimization histories for the parents of the offenders in this sample was consistent with the findings of previous studies. The most glaring finding in the current study was that 92 percent of the sibling incest offenders had a history of being physically abused by one or both parents. This is consistent with O'Brien's (1991) findings that 61 percent of his sample of sibling incest offenders had physical abuse in their families. The study's finding that 58 percent of the sibling incest cases had been exposed previously, but continued following ineffective parental intervention, lends support to the pervasiveness of parental denial and minimization. Also, denial and minimization were evidenced by 42 percent of the sample being diagnosed as having conduct disorders and by 58 percent having shown behavioral problems in school. 1 table and 28 references