Skin conductance and heart rate of 19 drug-free acute schizophrenic patients were measured before neuroleptic therapy was started. The patients were divided into two groups according to therapeutic outcome. The Discriminant Analysis revealed a difference in the ANS activity pattern between the group with low improvement and the group with a more favorable outcome. The low improvement group showed a paradoxical ANS reactivity pattern: relatively lower activity in skin conductance level under demand (attention task) and relatively higher activity, as reflected by the cardiovascular response to neutral stimuli (orienting stimuli), which suggests poor adaptation of ANS arousal to the environment in these schizophrenics. This finding agrees with those reported in other short-term outcome studies that considered differences in ANS activity in a schizophrenic population. The authors' findings indicate that these differences in the ANS response in schizophrenics should be included in future biochemical and pharmacotherapeutic investigations on schizophrenia.