The relationship between specific distributions of isolated soleal vein thrombosis (SVT) and risk factors was investigated. The subjects included 93 patients with SVT diagnosed with ultrasonography. In the acute thrombus distribution, the thrombi of central veins were significantly more frequent than the thrombi of medial veins in the unilateral SVT. The thrombi of central veins were not more significantly frequent than the thrombi of medial veins in the bilateral SVT. The risk factors of bilateral SVT are considered to be different from that of the unilateral SVT.