An analysis has been made of 9 cases of a leiomyosarcoma of the small intestine that were treated from 1974 through 1989. In two patients (22.2%), a perforation was seen, and a case report of a 59-year-old woman is presented. Further, case reports of leiomyosarcomas in the Japanese literature from 1980 through 1989 were clinico-pathologically analyzed. The frequency of a perforation was found to be 8.6%, and the distribution of the perforated leiomyosarcomas was the same as for the non-perforated cases. The five-year postoperative survival rate was 41.2%. Of note is that 3 out of 10 patients that had survived for 5 years subsequently died of sarcomatosis.