Objective To ascertain whether the frequency of pelvic pain recurrence is reduced and time to symptoms recurrence is prolonged in women with symptomatic endometriosis undergoing conservative surgery and post‐operative hormonal therapy compared with women treated with surgery only. Pregnancy rates and time to conception in women wanting children were also evaluated. Design A multicentre, prospective, randomised controlled study. Setting Nineteen Italian academic departments and teaching hospitals specialising in reparative and reconstructive surgery. Population A total of 269 women undergoing conservative surgery for mild to severe symptomatic endometriosis. Methods After surgery the women were assigned to treatment with subcutaneous goserelin depot injections for six months or to expectant management. Dysmenorrhoea, deep dyspareunia, nonmenstrual pain and general discomfort were graded according to a verbal rating scale from 0 (absent) to 3 (severe) and the scores summed to give a total symptoms score. Only patients with at least one preoperative moderate or severe symptom were enrolled. The women were evaluated regularly for two years. Main outcome measures Post‐operative pain recurrences (total symptoms scores ≥ 5), time to recurrence, pregnancy rates and time to conception in the two study groups. Results At oneand two‐year follow up visits, 14/107 (13.1%) and 19/81 (23.5%) patients had moderate or severe symptoms recurrence in the goserelin group compared with, respectively, 22/103 (21.4%) and 27/74 (36.5%) in the expectant management group (P= 0.143 at 1 year and 0.082 at 2 years). Time to symptoms recurrence was significantly longer in the goserelin group according to survival analysis (Wilcoxon test, P= 0.041). Among women wanting children, few conceptions occurred in both the goserelin (8/69, 11.6%) and the expectant management group (14/76, 18.4%). There was no significant difference at survival analysis (Wilcoxon test, P= 0.427). Conclusion Post‐operative treatment with goserelin significantly prolonged the pain‐free interval after conservative surgery for symptomatic endometriosis and did not influence reproductive prognosis.