Objective— To observe if a combination of a depot GnRH agonist and cyclical hormone replacement therapy decreases menstrual b od loss. Design— open, observational study comparing the objective assessment of menstrual blood loss before, during and after 3 months treatment. Subjects— 20 women with a subjective complaint of heavy menstrual loss in whom no cause could be discovered. Interventions— Each woman received 3 months of depot goserelin (Zoladex) combined with cyclical hormone replacement therapy (Cyclo-Progynova, 1 mg). Menstrual loss and symptoms were assessed before, throughout and after the study. Main outcome measures— Changes in objective and subjective assessments of menstrual blood loss and the acceptability of the treatment. Results— The median pretreatment menstrual loss was 68 ml (range 23–397). Only 8 (40%) of the patients had a loss exceeding 80 ml per period. The median blood loss was 30 ml, 16 ml, and 17 ml in the three treatment cycles (P < 0.001 Wilcoxon rank sum for the third cycle). There was a significant decrease in the median length of menstruation (P < 0.001) and the number of towels or tampons (P < 0.01) used per period in the third treatment cycle. There was a significant decrease (P < 0.005) in the number of women complaining of dysmenorrhoea, premenstrual symptoms, flooding and the passage of clots. Seventeen patients experienced hot flushes. Eighteen of the 20 patients were completely satisfied with the treatment and would have been happy to continue with it for longer than 12 months. Conclusions— The combination of a depot gonadotrophin releasing hormone agonist and cyclical hormone replacement therapy is a successful and acceptable treatment of dysfunctional uterine bleeding.