Objective To investigate which clinical characteristics at baseline are predictive for great saphenous vein recurrence following ultrasound-guided foamsclerotherapy. Material and methods Data of patients treated for great saphenous vein incompetence with ultrasound-guided foamsclerotherapy were derived from a multicentre prospective randomized controlled trial comparing surgery versus ultrasound-guided foamsclerotherapy with a follow-up of two years. Recurrence of reflux was determined on colour duplex scans at three months, one year and two years. Univariate and multivariate Cox regression analysis was used to evaluate the effect of gender, age, C of CEAP classification, diameter of great saphenous vein, injected foam volume, presence of distal great saphenous vein reflux, presence of reflux in the anterior accessory saphenous vein and Venous Clinical Severity Score on risk of recurrent reflux. Results Two hundred twenty-five patients were available for analysis. Treatment after one single session was successful in 120 patients and recurrence of saphenous reflux was observed in 105 patients within two years during follow-up. Significant associations with risk of recurrence were observed for mid thigh great saphenous vein diameter (HR=1.012 with 95% CI: 1.002-1.022, p=0.022) and presence of distal great saphenous vein reflux (HR=1.882 with 95% CI: 1.029-3.443, p=0.040). Conclusion In conclusion, this prospective study suggests that ultrasound-guided foamsclerotherapy treatment for the proximal great saphenous vein is less effective for patients with a large vein and a refluxing distal great saphenous vein at baseline.