PURPOSE: Sarcomas arising in intraperitaneal cavity and retroperitoneal space are relatively uncommon. Thus, studies characterizing the results of long-term follow-up are limited. The purpose of this study was to identify the clinicopathologic features and prognostic factors of intraperitoneal and retroperitoneal sarcomas. Materials and Method: Thirtyeight patients with intraperitaneal or retroperitoneal sarcoma who had been treated at Department of Surgery, Korea Cancer Center Hospital during the period from January 1987 to December 1997 were reviewed retrospectively. RESULTS: The ratio between male to female was 0.9: 1. The mean age of the patients was 48.3 (32-75) years. The most common symptom was abdominal pain or discomfort (61%), followed by palpable mass (55%), GI bleeding (34%), weight loss (26%), and change of bowel habits (21%). The most comman histologic type was leiomyosarcoma (73.7%), followed by liposarcoma (23.7%), and malignant fibrous histiocytoma (2.6%). The mean tumor size was 15.5 x12.1 x 8.7 cm. Among 38 cases, 25 cases developed in intraperitoneal cavity and 13 cases arose in retroperitoneal space. Overall, 44 operations were performed in 31 patients. Among them, complete surgical resection constituted 73%. In 20 cases, combined resection of adjacent organ was performed to accomplish complete surgical resection of tumors. During the median follow up period of 23 months (3~116 months), the overall 5-year survival rate was 34.7%. The patients who had been treated by complete surgical resection showed better survival than those in whom palliative resection or biopsy only was performed (38.6% vs 0% of 5 YSR, P=0.015). Liposarcoma showed better prognosis than leiomyosarcoma (41.7% vs 34.2% of 5 YSR, P=0.0000). The size of tumor (10 cm>vs 10 cm< or =) was not a statistically significant prognostic factor. CONCLUSION: In this series, The histologic type and complete surgical resection were important factors that can affect the survival of the patients. Aggressive surgical resections are therefore wananted to obtain better outcome of the patients with intraperitoneal and retroperitoneal sarcomas.