Aim of the study. To estimate the clinical efficiency and selected features of venous wall damage during endovascular electrocoagulation in the context of possible recanalization. Material and methods. Forty patients presenting with CEAP C2-C4 class primary varicosis underwent endovascular electrocoagulation of great saphenous vein with the use of a HVF-300-02 ElePS apparatus at 90 W and R 200 Ohm. The severity of lesions in the venous wall was estimated by histological methods. The degree of obliteration of great saphenous vein was determined in the ultrasonic study 5 days, 2 month, 1 and 3 years after endovascular electrocoagulation. Results. Occlusion of the treated vein occurred in 97.9, 96.5, and 89.5% of the cases 5 days, 2 month, and 1 year respectively after the electrocoagulation. One (5,3%) of the 19 patients experienced a relapse of the disease within 1 year after electrocoagulation. Histologically, lumen occlusion was apparent as a result of thermal injury and mural oedema in the absence of blood clot formation. Complications included 2 (5%) cases of skin surface burn and 2 (5%) cases of paresthesia in the medial ankle region. Conclusion. Endovascular electrocoagulation for the treatment of primary varicosis is a low-traumatic cosmetic surgical technique. Occlusion of the vein lumen during endovascular electrocoagulation occurs as a result of direct injury to the vascular wall without blood clot formation. It decreases the risk of relapse of the disease as a consequence of recanalization of the coagulated vein.