Frequency of aggression in 5- to 8-year-old children was examined in relation to frequency of helping, comforting and sharing. Subjects (39 boys and 40 girls attending a summer day camp) were each observed for two hours and their aggressive and prosocial behaviors recorded. This study differed from previous investigations of this issue in two respects: (1) individual differences in opportunities to help others were identified and statistically controlled; (2) assertive but nonaggressive behaviors were distinguished from behaviors intended to insult or injure and the importance of assertiveness as a predictor of prosocial behavior was assessed. Although assertiveness was positively and significantly related to prosocial behavior for boys and girls, no significant relations were identified between agression and prosocial behavior when the sample was split on sex alone. When the sex groups were subdivided into those above and below the respective group medians in aggression, significant negative relations between aggression and prosocial behavior emerged for both groups of boys, but only when number of opportunities to help others was controlled. For girls, there were no significant relations between aggression and prosocial behavior. Apparent discrepancies between the present findings and earlier reports of positive relations between aggressive and prosocial acts are explained and methodological refinements discussed. (Author/SB)