The gender differences in the development of prosocial and antisocial behavior of 164 Hong Kong Chinese adolescents were investigated over a two-year period. There were no significant differences between boys and girls, both concurrently and longitudinally, in prosocial behavior. However, boys were significantly more antisocial than girls at Grade 7, and the frequency of antisocial behavior showed little change from Grade 7 to Grade 9 in boys. On the other hand, girls demonstrated a significant increase in the frequency of antisocial behavior from Grade 7 to Grade 9. Finally, there were no significant gender differences in antisocial behavior at Grade 9. The gender difference in the development of antisocial behavior was explained in terms of puberty and child rearing pattern.

Key words: gender difference, prosocial behavior, antisocial behavior