With the aim of studying the frequency of Chagas' disease among sufferers of uterine leiomyoma, we analyzed women older than 35 years who underwent surgery and presented with leiomyoma on anatomicopathological examination. The diagnosis of Chagas infection was based on positivity to at least two of three serological tests: enzyme-linked immunosorbent assay, passive hemagglutination, and immunofluorescence. The study was case controlled, matching for age, skin color, and parity. The control group consisted of women undergoing surgery for other benign gynecological alterations. During this period, 118 women presented with uterine leiomyoma, 27.1% of whom were serologically positive for Chagas' disease versus 16.1% of the controls (P < 0.05). Matching by skin color and parity showed that 40% of the white multiparous women with uterine leiomyoma had Chagas' disease versus 10% of the controls (P < 0.05). We concluded that there appears to be an association between Chagas' disease and uterine leiomyoma.