Electrodermal activity was measured in recent-onset schizophrenic patients (n = 98) and matched normal control subjects (n = 40) as part of an ongoing longitudinal study. Results at the initial inpatient test were generally consistent with the current consensus in the literature. A large subgroup of the patients was found to be nonresponsive with the phasic skin conductance orienting response measure, whereas the remaining subgroup of patients was found to be electrodermally tonically hyperaroused. Heightened electrodermal activity at the inpatient test was associated with a number of symptoms in male patients and with poor recovery from the acute schizophrenic episode. Followup tests conducted when the patients were in states of remission and psychotic relapse revealed that tonic electrodermal arousal measures qualify as state-sensitive episode indicators, whereas phasic nonresponding may qualify as an atypical vulnerability indicator. Moreover, preliminary data from three patients suggest that increases in tonic electrodermal arousal may temporally precede psychotic relapses. The principal findings are consistent with a vulnerability/stress model that posits that electrodermal hyperarousal is part of a transient intermediate state that may lead to a psychotic episode in a vulnerable individual.