Aim. To study the possibilities of the application of the micronized purified flavonoid fraction for the treatment of secondary varicose veins in the small pelvis developing after iliac vein thrombosis. Material and methods. The present clinical study included 24 patients of whom 17 (71%) were men at the mean age of 54 years and 7 (29%) women (mean age 57 years). The average duration of thrombosis was 3.9 years. All the patients were offered a month-long course of the treatment with the use of the micronized purified flavonoid fraction at a daily dose of 1000 mg. The results of the comprehensive clinical and ultrasound studies carried out before the onset of therapy were compared with those obtained after the one-month treatment. Results. The mean diameter of paraprostatic veins in the male patients decreased significantly under effect of the treatment down to the normal values whereas the frequency of  retrograde circulation in the veins of the paraprostatic plexus decreased to 3 (18%). The number of women presenting with varicose veins in the small pelvis decreased to 6 (25%) under the influence of the treatment while the mean diameter of their parametrial veins decreased to almost normal value; the same is true of the frequency of the retrograde blood flow in the parametrial plexus veins. The clinical examination of the patients after the completion of the treatment has demonstrated positive dynamics of their condition. The number of patients complaining of pain in the small pelvis decreased from 8 (33%) to 1 (4%). Prior to the treatment, all the patients suffered from micturition disorders of different severity, with the mean IPSS value being 9.6 (95% CI 1—21). The number of patients with such condition decreased to 9 (38%) while its severity was relieved, with the mean international prostate symptom score (IPSS) being 3.8 (95% CI 0—19). Prior to therapy, three women presented with dyspareunia compared with only one after the treatment. Conclusion. The treatment with the use of the micronized purified flavonoid fraction at a daily dose of 1000 mg during one month leads in the men and women presenting with secondary varicose veins in the small pelvis developing after iliac vein thrombosis to the improvement of venous hemodynamics in the small pelvis and the reduction of clinical manifestations of the disorders in pelvic organs.