Electroencephalographic observations have been made on 30 patients, 15 of whom received convulsions by means of raw a. c., 15 by means of unidirectional fluctuating current; and it is suggested that there is a significant increase in the occurrence of slow wave formations in that group receiving raw a. c. when compared to the group receiving unidirectional fluctuating current. Five of the 30 cases have been found to show clinical abnormalities coinciding with electroencephalographic abnormalities and it is suggested that there is a relationship between these two phenomena. There is a possibility that cerebral dysrhythmia is more easily brought about following electroshock therapy in those patients who do not recover to the point of being well enough for discharge from a mental institution.The above findings are submitted as a preliminary report and the authors do not intend to infer that the series of patients observed is large enough to do more than suggest the relationships discussed in this paper.In addition to the patients treated in the research unit of the Toronto Psychiatric Hospital, the above series included patients from the Neuro-psychiatric Clinic of the Toronto Western Hospital by permission of Dr. H. K. Detweiler, physician-in-chief. The unidirectional electroshock unit is the property of the Toronto Western Hospital.Abstract Teaser