This prospective and multicenter study shows the results at 1 year of radiofrequency-powered segmental thermal obliteration (RSTO) carried out with the ClosureFast procedure. The RSTO clinical and duplex ultrasound imaging results were evaluated at 3 days, 3 months, 6 months, and 1 year. All procedures were carried out on outpatients under tumescent local anesthesia. Among the 295 members who were treated, 289 were reexamined at 3 days, 290 at 3 months, 289 at 6 months, and 220 at 1 year. Occlusion scores were 99.7%, 99.3%, 98.6%, and 96.9% at, respectively, 3 days, 3 months, 6 months, and 1 year. At 3 cm below the saphenofemoral junction, before the procedure, the greater saphenous vein (GSV) diameter was 5.4+/-2 mm (range 2-18). It decreased to 4.5+/-1.7 mm at 3 days, 2.4+/-1.5 mm at 6 months, and 1.3+/-0.9 mm at 1 year. In members reexamined at 1 year, the decrease in diameter of the treated vein compared with the preprocedural measurement was 79% (p<0.001, t-test). At 1 year, in 58% of the cases, duplex ultrasound imaging at mid-thigh level could not show the GSV trunk. Preprocedural pain that was present in 57.5% of the cases decreased to 10.8% of the cases at 3 days and 2% of the cases at 1 year (p<0.001, chi2 test). Among the treated limbs, 70.1% did not present with any postprocedural pain at any time of the follow-up. On the third day, the patients evaluated the mean pain intensity at 0.7+/-1.6 on a visual analog scale of 0-10. During the follow-up, no painful indurations were noticed in 67.7% of the legs. No thromboembolic complications were reported. Paresthesias were observed in 3.4% of the cases. Invalidity clinical score, evaluated at 3.9+/-2 before the procedure, decreased to 3.5+/-1.2 on the third day, 0.9+/-1.5 at 3 months, 0.7+/-1.2 at 6 months, and 0.5+/-1.1 at 1 year. This study confirms the efficacy of RSTO when using ClosureFast, which allows obliteration of the GSV trunk in 97% of cases at 1 year with few side effects and almost no postprocedural pain.