Seventy-nine postmenopausal patients received aminoglutethimide (AG; 750 mg daily) and hydrocortisone therapy for metastatic or locally recurrent breast cancer following the failure of other hormonal therapy. Fourteen of 64 patients, tolerating the drug and assessable for response, achieved a complete or partial response. Disease stabilisation occurred in a further 2 patients giving a response rate of 25% in these patients. Median duration of response was 10 months. Response rates to AG were not significantly different whether or not there had been a response to previous hormonal therapy but a trend to higher response rates in ER rich tumours was observed. Those with a longer interval from first relapse to the start of AG appeared more likely to respond. Side-effects were noted in 35 patients overall (44%) and in 70% of those over the age of 65 years. Treatment was discontinued because of toxicity in 10 patients and there was one death due to agranulocytosis. AG is active in postmenopausal breast cancer following failure of first-line hormonal therapy, toxicity limiting its use earlier in the disease.