In our varicose vein center, on a trial basis, among the patients with asymptomatic calf deep vein thrombosis (CDVT) we carefully selected the patients for varicose vein surgery using the requirements as follows; 1) the patients had varicose veins with incompetent saphenous veins, 2) sequential examination including DUS confirmed stability and clinical insignificance of asymptomatic CDVT, 3) the patients do not have any risk factors for DVT such as a coagulation profile disorder (antithrombin deficiency, protein C deficiency, protein S deficiency, or antiphospholipid syndrome) or malignancies, 4) surgery is possible under local anesthesia alone, and 5) the patients can understand the concept of asymptomatic CDVT and undergo the surgery on their own will and informed consent. The patients who fulfilled these conditions underwent the varicose vein surgery. Twenty-eight patients with 30 limbs with varicose veins had asymptomatic CDVT, found by preoperative duplex ultrasonography (DUS). Among CDVT, 91% of CDVT existed in the soleal veins. After the diagnosis of the asymptomatic CDVT, serial DUS was performed and showed no changes in the status of the thrombus. Then varicose vein surgery (high ligation of the saphenous junctions either with or without stripping of the saphenous veins) was performed. After the surgery, the CDVT was re-evaluated by DUS. In 27 limbs, CDVT did not show any changes in the status of the thrombus, and in 3 limbs the CDVT was partially resolved. These data suggest that, at least, as far as the patients fulfilled these conditions, varicose vein surgery did not worsen the asymptomatic CDVT. (This is a translation of Jpn J Phlebol 2016; 27: 405-412.).