Recent research on the disorders of attention and activity has indicated inherited variants ofgenes controlling aspects of neurotransmission, abnormalities of structure and function in regionsof frontal lobes and basal ganglia, failures to suppress inappropriate responses, and a cascade offailures in various kinds of cognitive performance and organization of behavior. This reviewintegrates the neurodevelopmental findings with findings from developmental psychopathology.It outlines several developmental tracks by which constitutional factors interact with thepsychological environment. In one set of tracks, altered brain states lead to cognitive alteration.An understimulating environment is evoked by (and may be genetically associated with) aninattentive and cognitively impulsive style during early childhood. In another track, impulsiveand inattentive behavior shows direct continuity through childhood into late adolescence. In yetanother track, impulsiveness evokes (and may be genetically associated with) critical expressedemotion from parents and inefficient coping strategies, which in turn contribute to thedevelopment of antisocial conduct. This formulation emphasizes the need for several types ofresearch: the mapping of biological findings onto different components of disorder, thecombination of genetically informative designs with direct measurement of relevant aspects ofthe environment, and the use of longitudinal studies to examine predictive and mediating factorsseparately for different aspects of outcome.