Objectives: The aim of our study was to analyze prognostic factors in gastric leiomyosarcoma. Method: We retrospectively reviewed the medical records of 33 patients with pathologcally proven leiomyosarcoma diagnosed from 198l through August 1995. All 33 gastric leiomyosarcoma were histologically confirmed by the pathologist. The factors analyzed are patient age, sex, tumor location, surgical procedure, tumor size, histologic grade, p53 and nm23. Expression of p53(positive vs. negative) and type of nm23 expression(diffuse vs. granular) were measured by immunohistochemical staining in 25 surgically resected specimens. The survival curves obtained by Kaplan-Meyer methods were compared using Log-rank test. Result: The 33 patients represents 0.39% of all patients with 8370 gastric cancer patients presenting during the same period. There were 23 males and 10 females. The mean age at the time of diagnosis was 57 years. Forty percent(13/33) of the tumors were located in the body, 30% (10/33) in fundus and 21%(7/33) in cardia of the stomach. Only three tumors(9%) were located in the antrum. Twenty seven of these tumors were treated by radical gastrectomy and 6 were treated by wedge resection. Histologically, 34.9% were low grade and 65.1% were high grade. Metastatic involvement was noted in four of patients at the time of diagnosis. p53 overexpression was positive in 28%. nm23 expression was positive in all cases; 72% were diffuse type and 28% were granular type. The 5-year survival rates of all cases were 79% and the 5-year disease free survival rates were 52%. Among the factors analyzed, the tumor size was the only significant prognostic factor. 5 year survival rete was 100% for tumors less than 10cm(n=16) and 55% for tumors larger than 10cm(n=l7). Tumor size and tumor grade were significant prognostic factor in disease free surviva. Conclusion: Our data suggest that leiomyosarcoma representing very small portion of gastric cancer were more commoly located in the upper part of stomach. Variables such as age, sex, tumor lacation, type of surgery, p53 overexpression and type of nm23 expression did not have prognostic significance. Tumor size was the only significant prognostic factor in overall survival(p<0.05). Tumor size and tumore grade were significant factors in disease free survival(p<0.05). The authors believe that these data will provide selection criteria for future clinical studies.