Research on the “cycle of violence” is hampered by significant methodological difficulties intrinsic to family violence research. The vast majority of both child abuse and interpersonally violent acts are never reported, leave no archival trace, and involve only two witnesses: the victim and the perpetrator. Therefore, research on the cycle of violence requires development of valid, self-report assessments of both childhood abuse and of perpetration behaviors. The article details the development of the API, a comprehensive self-report instrument that assesses childhood sexual and physical abuse as well as four types of perpetration in male subjects. The validity of the API has been demonstrated through follow-up interviews that indicate high cross-method concordance rates, and in the results of six studies in which abuse and perpetration have been associated with theoretically predicted outcomes. Tables, references, appendix