Cognitive-neuropsychological tests were given to adolescent boys (N = 177) to investigate processes associated with physical aggression. Factor analysis yielded 4 factors representing verbal learning, incidental spatial learning, tactile-lateral ability, and executive functions. Physical aggression was assessed at ages 6, 10, 11, and 12, and 3 groups were created: stable aggressive, unstable aggressive, and nonaggressive. The authors found main effects for only the executive functions factor even when other factors were used as additional covariates in a step-down analysis; nonaggressive boys performed better than stable and unstable aggressive boys. The covariates family adversity and anxiety were both related only to the verbal learning factor. This study highlights the importance of deficits in executive function in the expression of physical aggression relative to other cognitive-neuropsychological functions.