Aim. To estimate the effectiveness and practicability of endovenous laser ablation of incompetent perforating veins in the patients presenting with postthrombotic symdrom (PTS) and the closed throphic ulcers on the lower extremities. Material and methods. A total of 41 patients with functional class C5  PTS were examined and treated. They were divided into two groups. The study group was comprised of 20 patients selected for endovenous laser ablation of incompetent crural perforating veins with the use of the apparatus operated at a wavelength of 940 nm in the pulsed regime with a pulse power of 15 W and duration of 1 second. The diameter of the perforating veins varied from 0.2  cm to 0.84 cm (mean 0.39 cm). The number of pulses delivered into the venous lumen varied from 5 to 40 (mean 9). At least five pulses were delivered into a perforating vein with a diameter below 0.3 cm, at least 20  pulses into the a vein with a diameter of 0.4—0.6 cm, and from 25 to 40 pulses into the veins with a diameter of more than 0.6 cm. The control group included 21 patients given only the conservative treatment. Results. The results of angioscanning indicate that complete ablation occurred in 48 (78.6%) perforants within 3 days after the treatment. No complications related to the laser-assisted intervention were documented in the postoperative period. A relapse of trophic ulceration developed one year after surgery in 6 (30%) patients of the study group and in 7 (33%) ones in the control group (p=0.819). Venous lumen recanalization in conjunction with the development of recurrent reflux was documented in 39 of the 48 (81%) successfully ablated perforants. Conclusion. Endovenous laser ablation of incompetent crural perforating veins does not reduce the frequency of recurrence of trophic ulcers in the patients presenting with postthrombotic syndrom. The technical effectiveness of endovenous laser ablation in the patients with these conditions is rather low whereas recanalization of the perforating vein lumen occurs in the majority of the cases.