The authors evaluated the long-term results of sclerosing therapy as an alternative to surgery by means of high-resolution US and Doppler dynamic fluximetry (duplex system). Seventy patients (53 females and 17 males) were examined, all of whom fulfilled the clinical criteria of recovery and efficacy of sclerosing therapy. Average follow up was 20 months (range: 6-26). The results, compared with duplex findings before sclerosing therapy, demonstrated: a) persistence of reflux and absence of US signs of sclerosis (9/70 patients); b) evident sclerosis with persistent residual lumen and reflux of variable entity at the thigh (33/70) cases; c) incomplete sclerosis sparing the crosse, with physiological flow and disappearance of reflux (8/70 patients); d) nearly complete sclerosis with vasal lumen obliteration (20/70 cases). No changes were observed in the deep venous system after sclerosing therapy. The authors stress the advantages of the duplex system they employed as an instrumental support to clinics for a complete monitoring of sclerosing therapy.