SUMMARY In this case report we describe a 44 year old man who developed a transient increase of CSF protein in association with a course of electroconvulsive therapy for depression. Neurological evaluation failed to show any other abnormalities. The finding seems to reflect a transient dysfunction of the blood-brain barrier.Electroconvulsive therapy (ECT) is thought not to increase CSF protein (Essman, 1973). Neither patients who underwent a course of ECT (Jacobs, 1944;Eiduson et al., 1960) nor experimental animals (Spiegel-Adolf et al., 1945) (Jacobs, 1944).In this report we describe a physically healthy, depressed patient who developed an increase in CSF protein after a course of ECT. The CSF protein returned to its previous values shortly after ECT days without drugs, he had a 27 day trial of amitriptyline 250 mg daily. Because of poor antidepressant response the drug was discontinued, and a course of 11 ECT sessions was administered at a frequency of three treatments per week with good antidepressant response. However, he relapsed within a week and was given one ECT weekly for three consecutive weeks. He was discharged without symptoms and advised to return to work and to have maintenance ECT bimonthly as an outpatient. Three months after discharge he remained asymptomatic, had no physical complaints, and reported that he functioned well at work. As part of a continuing study of depression the patient had undergone lumbar punctures during the drugfree period and during amitriptyline treatment. On both occasions the CSF was clear with no cells and normal glucose values. Protein values were 0.42 and 0.64 g/l respectively, measured by turbidimetry (Tietz, 1976). A third lumbar puncture, performed three days after the eleventh ECT, revealed a CSF protein of 0.94 g/l, while the rest of the CSF values remained normal. A repeat cytological examination, CSF immunoelectrophoresis, sedimentation rate, cryptococcal antigen, skull and spine radiographs, EEG, 99Tc brain scan, and CAT scans with and without contrast enhancement were normal. Another lumbar puncture performed 13 days after the last ECT showed a decrease of CSF protein to 0.6 g/l, with no cells and normal glucose.