In a study designed to evaluate the state of arousal and the autonomic reactivity to experimental conditions in schizophrenic patients, 12 acute, unmedicated schizophrenic patients with paranoid hallucinatory symptomatology and 63 healthy normal control subjects were administered four standardized tasks: cold pressor test, noise, mental arithmetic, and active relaxation. Biochemical (norepinephrine and cortisol) and physiological (electromyogram, electroencephalogram, skin and conductance response, skin conductance level, finger pulse amplitude, finger temperature, heart rate, respiratory volume, pulse wave velocity, and electrogastrogram) parameters were measured simultaneously. Schizophrenic patients showed elevated levels of cortisol and norepinephrine, as well as heightened responsivity on measures of electromyographic activity, skin conductance level, and heart rate, throughout the trial, and reduced responsivity to conditions of stress. It is concluded that schizophrenic patients show higher nonspecific activation and reduced ability to react to external stimulation, perhaps induced by lack of inhibition of the reticular formation by the limbic system.