Aggressive conduct disorder, defined broadly on the basis of fighting, disobedience, destructiveness, and meanness, was diagnosed in 65 out of 136 boys and 17 of 43 girls consecutively admitted to a psychiatric clinic. Psychotic, brain damaged, and seriously retarded children were excluded from the series. Boys and girls with conduct disorder differed significantly from those with other diagnoses on a number of noncriterion symptoms, particularly those grouped as reactive and egocentric. Boys with conduct disorder were more often involved in antisocial behavior, girls in precocious sexual behavior. The study presents a more detailed clinical picture of the disorder, and suggests that the presence of specific antisocial behavior may be a useful criterion for dividing affected boys into two roughly equal subgroups.