Studied the relation between cognitive functioning, as evidenced by IQ and achievement test performance, and Diagnostic and Statistical Manual of Mental Disorders (DSM-III) categories of conduct disturbance, using data from Black adolescents who were members of collaborative perinatal project from birth to age 7 yrs. At age 17 yrs, Ss and their parents were administered a battery of instruments that included standardized psychiatric diagnostic interviews as part of a call-back study. Analyses were compatible with the hypothesis that deficiencies in cognitive functioning are causally related to adolescent conduct disorder as defined by DSM—III. Results suggest that the relation of cognitive functioning to psychiatric status was specific to conduct disorders. Results were incompatible with the hypothesis that conduct problems lead to deficits in cognitive functioning. The 3 most important factors in accounting for age-17 conduct disorder were cognitive functioning, parent psychopathology, and early aggression.