Objective. The objective of the present study was to elucidate the specific features of small pelvis vein lesions following iliac vein thrombosis. Material and methods. A total of 70 patients: 46 (65.7%) men and 24 (34.3%) women who had experienced iliac vein thrombosis 3.8 years (on the average) before the onset of the study were available for the examination. All the patients underwent duplex scanning of the small pelvis veins that revealed venous dilatation of various degree in  48 (68.6%) patients. Grade I dilated pelvic veins (0.5—0.6 cm) were found in  13 (27.1%) patients, Grade II (0.7—0.9 cm) in 28 (58.3%) cases and Grade III (0.9 cm or more) in 7 (14.6%) observations. Grade I, II, and III venous dilatation was documented 1—3 years after thrombosis in 7 (40.0%), 6 (42.9%), and 1 (7.1%) patients respectively. Grade II dilatation of small pelvis veins prevailed 3—5 years after thrombosis (16 or 76.2% patients) whereas Grade I and III dilatation was found at this time in 3 (14.3%) and 2 (9.5%) patients respectively. The occurrence of Grade III dilatation increased to 30.8% five and more years after thrombosis when the frequency of Grade II dilatation decreased to 46.2% and that of Grade 1 venous dilatation was observed only in 23.1% of the patients. Moreover, the women had varicose veins of the parametral and vesicular plexuses. All women presenting with varicose veins of the vesicular plexus had the  concomitant venous dilatation in the parametral plexus. The men who had experienced iliac vein thrombosis during the preceding period also experienced thrombosis of small pelvis veins largely in the paraprostatic plexus. Conclusion. Varicose veins of the small pelvis occur in 68.6% of the patients following iliac vein thrombosis. Most women suffer venous dilatation in the parametral plexus while in men veins of the paraprostatic plexus are most frequently affected with the formation of retrograde blood flow in 72.9% of the cases.