Objective. To study the effectiveness of heparinoid sulodexide in complex therapy of patients with endometrial dysfunction and concomitant undifferentiated connective tissue disease (UCTD). Patients and methods. We examined 88 patients with UCTD and endometrial dysfunction (the «thin endometrium» phenomenon). The therapeutic regimen of 41 patients (group 1а) additionally to cyclical therapy with 17-b estradiol and didrogesterone was supplemented by continuous heparinoid sulodexide for 3 menstrual cycles (MC), 20 patients (group 1b) in addition to cyclical therapy received the heparinoid from the 5th day of MC until the 7th day after ovulation, 27 patients of the reference group (group 2) received only cyclical therapy without heparinoid supplementation. Results. In patients of groups 1а and 1b, restoration of M-mode echo values ≥7mm was obtained in 71–73% of cases, the median endometrial thickness in group 1а increased by 2.8 mm, in group 1b – by 2.25 mm, in group 2 – only by 1.9 mm. The continuous intake of, including during menstruation, was not associated with an increase in blood loss nor changes in red blood counts. As was also found, in patients with UCTD who had algomenorrhoea with ultrasonic signs of varicose veins of the uterus administration of sulodexide resulted in a decrease of the severity of pain syndrome up to its complete disappearance. Conclusion. The treatment regimen for patients with endometrial dysfunction concomitant with UCTD НДСТ with inclusion of continuous heparinoid sulodexide (without a break during menstruation) enhances the effectiveness of therapy, does not involve a higher menstrual blood loss, and also has a positive effect on the severity of algomenorrhoea. Key words: algomenorrhoea, undifferentiated connective tissue disease, sulodexide, chronic endometritis