One hundred and forty-three patients with uterine leiomyosarcomas treated at Radiumhemmet from 1936 through 1981 were reviewed. Clinical and histopathological findings were analysed by bivariate and multivariate analyses to assign prognostic factors. Mitotic count, menopausal status and stage showed to be significant predictors of survival. The series was divided into two periods of time and a significantly higher survival rate in the second period was noted for patients with stage I disease. Thirty-seven patients with tumors showing less than 10 mitotic figures per 10 high power fields had a 5-year survival rate of 65% compared with 17% for 106 patients with 10 or more mitotic figures per 10 high power field. No significant predictor of a bad outcome for these low mitotic count tumors was found.