Eighty-five non-referred school children were divided into four groups based upon the IOWA Conners Teacher's Questionnaire: pure hyperactive (HYP), pure aggressive (AGG), mixed hyperactive/aggressive (HYP/AGG), and normal controls. The groups were compared on neurobehavioral tests believed to assess inattention and impulsivity. A continuous performance test indicated that the HYP group was more inattentive than the other groups and the HYP/AGG group was most impulsive. The AGG group did not differ from controls. The data support the distinction between HYP, AGG and HYP/AGG groups of children selected by the IOWA Conners.