Progestagen therapy following primary surgery for endometrial cancer has been advocated to reduce the risk of recurrence. The objective of this review was to assess the effect of adjuvant progestagen therapy in endometrial cancer.We searched the Cochrane Gynaecological Cancer Group trials register and MEDLINE up to May 1999.Randomised trials of progestagen therapy in women who have had surgery for endometrial cancer.Trial quality was assessed and two reviewers abstracted data independently.Six trials involving 4351 women were identified. Three trials included women with stage one disease only, whereas three included women with more advanced disease. Based on five trials, overall survival was not improved by adjuvant progestagen therapy (OR 1.05, 95% CI 0.88 to 1.24). Endometrial cancer deaths and relapse of disease appears to be reduced by progestagen therapy OR 0.88 95% CI (0.71-1.1) and 0. 81 95% CI (0.65-1.01) respectively. However, non-endometrial cancer related deaths were more common in women treated with progestagens OR 1.33 (1.02-1.73).Current evidence does not support the use of adjuvant progestagen therapy in the primary treatment of endometrial cancer.