Uterine sarcomas are uncommon malignancies. We retrospectively examined 24 cases of "high grade" endometrial stromal sarcomas (ESS). The histologic diagnosis was made if there was a high grade sarcoma with a high mitotic index and nuclear anaplasia. Heterologous elements could be present, if focal only. Leiomyosarcomas, mixed mesodermal sarcomas, and carcinosarcomas were excluded. Mitotic index was expressed as the number of mitoses per 10 high-power fields in active areas. Tumor grade was based on nuclear anaplasia. ESS were 5.7% of all uterine sarcomas. Median age was 58.2 years; median duration of symptoms was 67.5 days. Abnormal bleeding was the presenting complaint in 91.7%. Uterine enlargement was seen in 33%; protrusion through the cervical os was seen in 9 cases. Total abdominal hysterectomy and bilateral salpingo-oophorectomy was performed in 95.8%. Twenty patients had myometrial involvement; 5 patients had serosal spread and extrauterine disease; residual disease was seen in 3 patients. Adjuvant radiation was not beneficial. Ten patients had recurrences: 60% in the pelvis, 50% each with subcomponent of abdominal or distant disease. Overall survival was 3.4 years and was significantly associated with extent of disease, size of the primary tumor, and grade.