e23552 Background: Surgery with negative resection margins is now considered the main treatment for retroperitoneal sarcomas improving the survival and quality of life of patients. The most common obstacle to surgery with R0 resection in locally advanced tumors is the involvement of the great vessels. The purpose of this study was to analyze the results of surgical treatment in patients with locally advanced retroperitoneal sarcomas involving the inferior vena cava or iliac veins. Methods: The study included 34 cancer patients who underwent tumor resection with major vessel resection in 2015-2021. The mean tumor size was 15.5 cm (from 6 to 41 cm). The most common tumors were moderately differentiated liposarcoma (38%) and pleomorphic liposarcoma (26%). Results: Resection of the inferior vena cava was performed in 19 cases, resection of the iliac segment - 15. Circular vein resection without reconstruction was performed in 5 patients, wedge resection - 7, segmental resection with end-to-end anastomosis - 1, replacement of the venous segment with a prosthesis - 25. Resection of adjacent organs was required in 26.5% of surgical interventions. According to the final pathoanatomical examination, the rate of complete tumor resections (R0-1) was 88.2%. During the 30-day postoperative period, mortality and complication rates were acceptable, 29% and 0%, respectively. During the follow-up period, the median disease-free survival was 13 months, and the median overall survival was not reached. Conclusions: Surgical interventions expanded due to resection of the major veins in locally advanced retroperitoneal sarcomas allow achieving a high rate of radical tumor resection and improving relapse-free and overall survival rates.