The purpose of this study was to determine the correlation, if any, between the status of the somatosensory evoked potential (SEP) and functional change in the right upper extremity of patients with right hemiplegia following stroke. Sixty-eight such patients were admitted to a rehabilitation hospital for intensive treatment from 3 to 8 weeks after onset. All had SEP studies by stimulation of the median nerves of the upper extremities and had complete medical, neurologic and functional evaluations. Forty-two patients had an absent SEP; of these only one showed some functional gain in the right upper extremity (RUE) at discharge. Of 14 patients having diminished SEP, 5 (36%) had some functional gain in RUE at discharge. Of 8 having normal SEP, 3 (38%) showed some functional gain on discharge. None of these 64 patients had any function in RUE on admission. Four patients had a normal SEP and some function on admission, with an increase of function on discharge. Of right hemiplegic patients who showed absence of SEP and nonfunction of RUE on admission, 98% gained no functional return in RUE during hospitalization. These data suggest that SEP studies in stroke patients offer useful information for prognosis and rehabilitation programming.