From 1982 to 1987, 114 patients underwent operation at Memorial Sloan-Kettering Cancer Center for soft-tissue sarcoma of the retroperitoneum. A retrospective analysis of these patients defines the biologic behavior, surgical management of primary and recurrent disease, predictive factors for outcome, and impact of multimodality therapy. Complete resection was possible in 65% of primary retroperitoneal sarcomas and strongly predicts outcome (p less than 0.001). The rate of complete resection was not altered by histologic type, size, or grade of tumor. These patients had a median survival of 60 months compared to 24 months for those undergoing partial resection and 12 months for those with unresectable tumors. Forty-nine per cent of completely resected patients have had local recurrence. This is the site of first recurrence in 75% of patients. These patients undergo reoperation when feasible. Complete resection of recurrent disease was performed in 39 of 88 (44%) operations, with a 41-month median survival time after reoperation. Tumor grade was a significant predictor of outcome (p less than 0.001). High-grade tumors (n = 65) were associated with a 20-month median survival time compared to 80 months for low-grade tumors (n = 49). Gender, histologic type, size, previous biopsy, and partial resection versus unresectable tumors did not predict outcome by univariate analysis. Adjuvant radiation therapy and chemotherapy could not be shown to have significant impact on survival. Concerted attempt at complete resection of both primary and recurrent retroperitoneal soft-tissue sarcoma is indicated.