Objective: to improve the quality of diagnosis of the extent of ovarian cancer. Subjects and methods. The P.A. Herzen Moscow Oncology Research Institute operated on 500 patients aged 21 to 69 years with ovarian cancer. Prior to surgery, all the patients underwent ultrasound scanning of the abdominal cavity, small pelvis, retroperitoneal space, supraclavicular and inguinal areas, by using expert-class ultrasound equipment with three types of transducers (a 2—4 MHz convex transducer, 7—9 and 9—12 MHz linear transducers, and a 5—8 MHz intracavitary transducer). Results. The data of preoperative ultrasound examination were compared with surgical findings in all the patients. Tumor involvement of ovaries was manifested as their enlargement in most cases. The tumors were structurally solid in 270 (54%) patients, solid cystic in 75 (15%), cystic in 100 (20%), and cystic solid in 55 (11%). Bilateral and unilateral ovarian involvement was noted in 458 (91.6%) and 42 (8.4%) women, respectively; primary preoperative diagnosis revealed peritoneal dissemination in 185 (37%) patients. Conclusion. All the patients were found to have changes in the ovaries, including a tumor in the unenlarged ovaries. However, some pathognomonic signs of dissemination were revealed slightly worse, which was due to the location of pathological foci behind the bone structures and with the isoechoic structure relative to the surrounding retroperitoneal fat.