Two groups of 16 patients with depressive psychosis took part in a controlled evaluation of electro-convulsive therapy (ECT). One group received six brief pulse unilateral shocks under conventional anaesthesia and muscle relaxation; the second group underwent the same procedure without receiving shocks. Outcome was assessed by a separate investigator using the Hamilton Rating Scale for Depression under double-blind conditions. The results showed that this form of ECT was only superior to the control treatment for one item in the scale, a finding which could have occurred by chance. The results suggest that the ECT pre-treatment procedure has an important therapeutic effect. This casts some doubt on current views of the effectiveness of electro-convulsive therapy in general, and of brief pulse unilateral ECT in particular.