The aim — to study the possibilities of endovenous electric welding during the comprehensive surgical treatment of acute ascending thrombophlebitis (AAT) of great saphenous vein (GSV).Materials and methods. The treatment results in the period from 2015 to 2017 are analysed. 22 patients with AAT GSV at the age from 25 to 69 years (mean age — 49.36 ± 2.75 years). There were 5 men (22.73 %), women — 17 (77.27 %). According to the international classification of the CEAP (Clinical Etiological Anatomical Pathophysiological) class C2 was diagnosed in 4 patients, class C3 — in 9, class C4 — in 3, class C5 — in 5, class C6 — in 1. AAT GSV care was carried out with the endovenous electric welding of thrombosed vein segment. As a source of current, a multifunctional device for electric welding of live tissues EK300M («Svarmed», Ukraine) was used. Treatment results clinical evaluation was carried out considering the signs of thrombophlebitis recurrence, inflammatory infiltrate reduction in the welded vein area, pain syndrome reduction or disappearance, chronic venous insufficiency symptoms. The stability of the occlusion was monitored by ultrasound duplex angioscanning.Results and discussion. Patients with AAT GSV treated with endovenous electric welding were discharged from the hospital on the 4th — 7th day (on average — 4.86 ± 0.23 day) after the operation. In the near future, recurrence of thrombophlebitis was not fixed. In 19 (86.36 %) patients at the time of discharge from the hospital, inflammatory infiltrate along the welded vein significantly decreased, in 3 (13.64 %) — the pain syndrome managed to be completely decreased. In all operated, according to ultrasound duplex angioscanning, there was a stable occlusion of the welded veins. At 6 — 12 months in 19 (86.36 %) patients, ultrasonic duplex angioscanning revealed fibrous degeneration of welded GSV, in 3 (13.64 %) — recanalization of GSV.Conclusions. Endovenous electric welding of thrombosed GSV in 86.36 % of cases provided complete occlusion, fibrous transformation of the welded vein, reduced trauma and improved cosmetic result of the operation.