This study provided the first empirical description of child and interviewer behaviors occurring within semistructured assessment interviews with children suspected of being victims of sexual abuse. Specifically, relationships between child and interviewer characteristics and interview credibility were examined. Using the Child Abuse Interview Interaction Coding System (CAIICS, Wood, 1990), 55 videotaped interviews of high-risk sex abuse cases seen at a multidisciplinary assessment center were behaviorally coded. Support was found for the interrater reliability and criterion related validity of the CAIICS was found. Results also revealed that children were initially rated as relaxed and displayed few emotional behaviors. Thus, the assumption that a credible disclosure of abuse must necessarily include the display of emotion by the child was not supported. Second, several behavioral differences between preschool and school-aged children were identified: however, no meaningful gender differences were found. Third, supporting evidence was found for both age and gender effects in judgments of interview credibility, with girls and school-aged children judged as more credible. Fourth, while the interviewer did engage in so called leading behaviors, these behaviors were not found to be related to rating of interview credibility. However, interviewer behaviors may have affected interview credibility through an intervening variable. Finally, implications, for further use of the CAIICS for examining interviewer-child interactions, evaluating standards of practice, and assisting with interviewer training are discussed.