SUMMARYData were collected on 175 admissions to a child psychiatry clinic, primarily through interviews with mothers, Forty‐nine per cent of the children were diagnosed as hyperactive and 46 per cent as unsocialized aggressive; 34 per cert had both disorders. Comparisons were made between the children who were hyperactive only, unsocialized aggressive only, hyperactive and unsocialized aggressive, and those with other diagnoses, on behavioral Males which were derived from the interview data but were relatively independent of the diagnostic criteria. On the scales of antisocial behaviour, egocentricity and reactivity, hyperactive and unsocialized aggressive children resembled those who were only unsocialized aggressive more than those who were only hyperactive. These results support earlier critisms of a broadly defined syndrome of hyperactivity. However, evidence was also found for a more specific hyperactive syndrome such as that proposed by Sandberg, Rutter and Taylor (1978