A total of 67 delinquent subjects were rated on degree of aggressiveness by their counselors. Behavioral reactions were monitored in a group argument simulation, and physical and behavioral reactions were measured during a frustration-aggression assessment. Subjects classified as powerful-aggressive (PA) by counselors were significantly less able in convincing their peers to accept their wishes. Subjects rated powerful and nonaggressive (PN) were less accurate and those labeled PA significantly more accurate in predicting their persuasive ability. The incidence of angry statements by weak and nonaggressive (WA) subjects was considerably lower than that of other groups. Subjects classified as PA and WN demonstrated higher baseline arousal. This level of arousal declined during performance from peaks reached during trials. Weak and aggressive (WA) subjects and those labeled PA emitted significantly more verbally aggressive statements during the frustration-aggression assessment. WN's reported significantly less arousal and anger on a self-reporting measure. While PA's were successful in reaching goals without aggressive behavior, they tended to be inappropriately aggressive in insulting or harassing situations. WA's responded similarly to PA's on the group argument simulation, but WA's reacted with less anger to harassment on the frustration-aggression assessment and reported less arousal. WN's proved as successful in convincing their peers as their larger counterparts. Members of this group tended to shut down during harassment on the frustration-aggression assessment. PN's were less effective in convincing their peers, but became less physiologically aroused and emitted the least anger on the assessment. The performance of PN's under harassment on the assessment did not decline. PN's did not report feeling upset; however, this was not supported by other measurements. Tabular data and 8 references are given.