Thirty-three consecutive admissions for schizophrenia with PSE diagnoses and free of neuroleptics were compared with 31 hospital staff for distinguishing features of bilateral electrodermal activity to a sequence of mild tones followed by a sequence of conspicuous tones with variation of temporal parameters. To mild tones most patients were either non-responders or non-habituators whereas most controls were habituators or non-habituators. To conspicuous tones patients as a group were more responsive but without the features of sensitisation to a test stimulus shown by controls. Patients as a group had more non-specific response and higher levels of skin conductance which showed less adaptation than controls. To a large extent previously reported difference in response latencies, rise-times and half-recovery times would appear to be a function of habituation rate. Patient -control differences may reflect anxiety and stress in patients, though lateral asymmetries in activity have a deeper salience for the nature of schizophrenia.