In a current study of autonomic nervous system (ANS) activity and attention has been assessed in 34 boys with diagnoses in the Disruptive Behavior Disorder (DBD) spectrum (Conduct Disorder, Oppositional Defian Disorder and/or Attention Deficit Hyperactivity Disorder (ADHD), selected for their antisocial and disruptive behavior, and in 33 normal control boys. We recorded skin conductance (SC) and heart rate (HR) during a rest period, a series of nonsignal tones, and a simple reaction time (RT) task. Attention was assessed by two RT tasks which have been used extensively in schizophrenia research: 1) Simple RT with constant and variable preparatory intervals, and 2) Simple, choice, and `crossmodal' RT to lights and tones. The DBD boys had higher HR but no differences in SC indices of `arousal'. However, they had smaller increases in all baseline measures to the onset of the RT task than controls. They were relatively more reactive to the RT stimuli in terms of SC amplitudes and latency, but habituated to them at a faster rate. These results are different from those obtained previously with more "pure" ADHD samples. Correlational analyses with behavior ratings suggest that there may be autonomically hyperresponsive and hyporesponsive subgroups who may show clinical differences somewhat oblique to the Conduct Disorder subdiagnosis. DBD subjects with low levels of metabolites of serotonin, norepinephrine, and dopamine measured from cerebrospinal fluid showed generally elevated ANS responsivity, particularly in the RT task. The RT tasks showed that DBD boys have particular problems when the timing or modality of the stimulus is uncertain. A 2-year clinical followup of these subjects revealed that low ANS baselines were predictive of institutionalization (HR, spontaneous SC fluctuations, SC level), suicide threats (SC level), and arrests (SC level).