After an episode of deep venous thrombosis (DVT) 123 patients were randomized into two groups: one was prophylactically treated with indobufen (60 patients), an oral antiplatelet agent, and one had no treatment (63) and acted as a control group. They were followed up for three years and scanned with color duplex scanning (CDS) every three months and any time that signs and symptoms suggested a new episode. In patients receiving indobufen the incidence of thrombosis was 5% in three years while it was significantly higher (46%) in the control group. Also 62% of the new episodes in the control group were asymptomatic (33.3% in the treated group). Results suggest that recurrent DVT is common, often asymptomatic, and confused with sequelae of the initial episode. The prophylaxis with indobufen is an effective measure in preventing recurrent thrombosis and avoiding the progressive deterioration of the deep venous system observed after deep venous thrombosis.