Thirteen women with symptomatic enlarged leiomyomatous uteri completed 6 months treatment with the gonadotropin releasing-hormone agonist (GnRH-a) buserelin, 600 micrograms daily subcutaneously (s.c.). Seven patients received injections (200 micrograms thrice daily, I-group) and six infusion by pump (50 micrograms.min-(1).2 h-(1). P-group). Residual uterine volumes after 6 months therapy were comparable in both study groups (I-group median 37%, range 23 to 74%; P-group median 49%, range 30 to 69%), as were estradiol levels. Symptoms were well controlled within short time. Six months posttreatment follow-up revealed uterine regrowth to pretreatment dimensions in all but 1 patient with recurrence of symptoms in most women. During therapy, several biochemical indices of bone metabolism were significantly elevated, reflecting an increased bone resorption; they were restored within 3 months after cessation of therapy, except for alkaline phosphatase. Triglycerides and HDL-cholesterol did not change during study; cholesterol was slightly, but significantly elevated after 6 months therapy. GnRH-a buserelin, 600 micrograms daily by s.c. injection or infusion is equally effective in reducing enlarged leiomyomatous uteri. Discontinuation of therapy is followed by uterine regrowth with recurrence of symptoms in most women. The present mode of therapy seems to be beneficial as an adjunct before myomectomy, or in advancing menopause in symptomatic, climacteric women.