The rationale for the use of anti-glucocorticoids in the treatment of major depression has been reviewed. Four patients with chronic severe depression who were resistant to conventional therapies were given RU 486 (200 mg/day) for periods up to eight weeks. Substantial levels of RU 486 were achieved within the first few days, and the levels fell gradually over the week after the treatment was discontinued. In three cases, treatment was stopped before the eight weeks were completed: in one case because of the appearance of a rash, in the others because of side-effects, which, in retrospect, were likely unrelated to the drug. The mean scores on the Hamilton Rating Scale for Depression of three patients decreased. Levels of adrenocorticotrophin, dehydroepiandrosterone and cortisol rose during treatment. These preliminary results suggest that glucocorticoid antagonists may be effective in the treatment of major depression and merit further exploration.