Sixty nine patients took part in a double-blind study to investigate the efficacy of bilateral, unilateral, and simulated ECT in the treatment of depressive illness. The findings suggest that both bilateral and unilateral ECT are highly effective treatments for depression and are significantly superior to simulated ECT. There was also evidence that patients receiving bilateral ECT recovered more rapidly than those receiving unilateral ECT and required significantly fewer treatments. The relevance of these findings to clinical practice is discussed.