Electrodermal arousal was studied at rest and during repetitive stimulation in chronic schizophrenics who were rated at either extreme of the Montrose Rating scale (MRS), either receiving a phenothiazine or no drugs, and in a control normal sample. Resting base level was significantly higher among Hi than Lo MRS, and among Nondrug than Drug patients: no patient sample was reliably below Control level. Nondrug patients showed no impairment in tonic arousal relative to Controls, even when such patients showed impaired phasic response (though the drug was seemingly associated with diminished tonic response). Considerable independence was demonstrated between phasic and tonic electrodermal functions. Unlike Controls (or Drug patients), Nondrug patients showed a general heightening of electrodermal arousal during repetitive innocuous stimulation. A vigilance hypothesis was offered suggesting that sensitivity to the general demands of the environment remains high among chronic patients, even where there may be a reduction in the input of specific items of information from that environment.The psychophysiological correlates of schizophrenia have been under study for several decades, and the pertinent literature has been reviewed repeatedly, most recently by Lang and Buss (1965) and by Stern and McDonald (1965).The results have been widely divergent and in frequent conflict. Schizophrenia has been associated with impairment in metabolic and endocrine functions as well as in autonomic and central nervous systems (Haskins, 1946) ; with "sluggish" sympathetic centers and parasympathetic dominance (Gellhorn, 1953); with deficient responsiveness in either, or both, sympathetic and parasympathetic divisions (Rubin, 1962); and with sympathetic dominance and excessive reactivity (Gunderson, 1953).Using electrodermal measures, the present study examines activation and adaptation among chronic, long-hospitalized schizophrenics. Earlier investigations of various components of autonomic arousal in chronic paauthor is indebted to Jacob Cohen for statistical guidance, to