Aminothiadiazole was used to treat 21 patients with metastatic or recurrent leiomyosarcoma of the uterus. All patients received a starting dose of aminothiadiazole of 125 mg/m2 intravenously (30-to-45-minute infusion), which was repeated at weekly intervals. All patients also took allopurinol 300 mg per day orally to prevent hyperuricemia, a side effect of aminothiadiazole. Five patients (25%) had stable disease but there were no objective responses. Toxicity was generally mild with this regimen. There was no life-threatening toxicity and only three episodes of severe toxicity. One patient experienced both grade 3 leukopenia and thrombocytopenia, while another patient had grade 3 nausea and vomiting. Further studies in this disease are not planned.