Recent research on the disorders of attention and activity has indicated inherited variants of genes controlling aspects of neurotransmission, abnormalities of structure and function in regions of frontal lobes and basal ganglia, failures to suppress inappropriate responses, and a cascade of failures in various kinds of cognitive performance and organization of behavior. This review integrates the neurodevelopmental findings with findings from developmental psychopathology. It outlines several developmental tracks by which constitutional factors interact with the psychological 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) an inattentive and cognitively impulsive style during early childhood. In another track, impulsive and inattentive behavior shows direct continuity through childhood into late adolescence. In yet another track, impulsiveness evokes (and may be genetically associated with) critical expressed emotion from parents and inefficient coping strategies, which in turn contribute to the development of antisocial conduct. This formulation emphasizes the need for several types of research: the mapping of biological findings onto different components of disorder, the combination of genetically informative designs with direct measurement of relevant aspects of the environment, and the use of longitudinal studies to examine predictive and mediating factors separately for different aspects of outcome.