Thirteen premenopausal women with uterine fibroids were treated for a maximum of 6 months with a long-acting agonist of luteinizing hormone-releasing hormone (LH-RH), goserelin (Zoladex depot, ICI Pharmaceuticals, Macclesfield, UK) 3.6 mg, administered subcutaneously every 28 days. A 55% reduction (range, 38% to 84%) in uterine volume assessed by ultrasound was obtained. The greatest reduction (30%) was apparent within the first treatment cycle regardless of whether treatment was started in the early follicular or the luteal phase. Fibroid regression was inversely correlated with urinary estrogen concentration. Treatment was well tolerated and only one subject withdrew from the study before its scheduled completion. Following cessation of therapy, ovulatory menstruation returned within 3 months in the majority of the subjects, but this was accompanied by a rapid regrowth of the fibroids. This medical approach to the management of fibroids merits further investigation but as yet cannot be regarded as an alternative to surgery.