This research aims at examining the relationships among unethical computer usage behavior and the personality characteristics of locus of control, adjustment to social norms, antisocial tendency, and aggression on Turkish university students. The research was applied to 217 university students. Data were collected through Unethical Computer Using Behavior Scale, Hacettepe Personality Inventory, Rotter's Internal-External Locus of Scale, and Aggression Scale. Data analysis was carried out by path analysis of structural equation models. The findings indicate that locus of control and antisocial tendencies had significant direct and indirect effects on unethical computer usage behavior, and social norms have significant indirect effects on it. The mediation variable determining all the indirect effects on unethical computer usage behavior was aggression. The aggression had direct effect and partial mediating effects on unethical computer usage behavior. The model containing these paths had acceptable and adequate fit values. (Contains 2 figures.)