The prosocial and antisocial behaviors of 2,862 Hong Kong Chinese adolescents were investigated. The major findings were as follows: (a) boys were more antisocial than girls: (b) negative peer influences were significantly stronger in boys than in girls, whereas positive peer influences were significantly stronger in girls than in boys; (c) antisocial adolescents tended to perceive their best friend as antisocial and exerting more negative influences on them, whereas prosocial adolescents tended to perceive their best friend as prosocial and exerting more positive influences on them; (d) antisocial behavior was positively associated with psychoticism and neuroticism; and (e) academic achievement tended to have a positive relation with prosocial behavior and a negative relation with antisocial behavior.