Tamoxifen, which is increasingly being used in breast cancer patients, has been associated with an elevated frequency of endometrial carcinoma. To our knowledge not a single case of uterine serous papillary carcinoma (USPC) has been documented during tamoxifen treatment. No conclusions as to a causal relationship are yet being made, but if it is due to tamoxifen, we should advise a strategy for prevention, because this subtype is not as curable as endometrioid carcinoma.