Uterine sarcomas are extremely rare uterine malignancies; with a review of the literature we could not find any data dealing with exogenous oestrogens or combined hormone replacement therapy (HRT) after leiomyosarcoma treatment. We report two cases of patients with leiomyosarcoma of the uterine corpus. Both patients were without pelvic irradiation or exogenous oestrogen treatment before the diagnosis. Leiomyoma of the uterus was found during surgery in both cases. Both patients were receiving HRT with non­conjugated oestrogens, after an intensive non-hormonal treatment had failed. No recurrence was established after surgical treatment in the patient with 12 mitoses per 10 high power fields (HPF). The patient is still on HRT (61 months). The other patient with a leiomyosarcoma with very high mitotic activity (40 mitoses per 10 HPF) received cytostatic and irradiation therapy after surgery because of locally widespread disease. Ten months after the diagnosis and 3 months after beginning HRT, recurrence was observed The patient thereupon stopped HRT. After two additional operations, the patient is alive and without evidence of disease. We presume that the present case reports observations might suggest that HRT did not appear to have a pronounced adverse effect on the leiomyosarcoma outcome in our patients. Nevertheless, until more collected data determine that HRT is safe, caution is needed.