The results of observations over 116 patients with nonorganic retroperitoneal tumors of the pelvis in the diagnosis of which computerized and ultrasonic tomography were used among other methods showed these methods to expand the possibilities of early diagnosis significantly. Analysis of 83 operations conducted on patients with nonorganic tumors of the pelvis revealed the main reasons why a radical operative intervention failed to be performed. Hemorrhage and pyo-inflammatory processes in the pelvic fat were the most common and serious complications in the postoperative period.