OBJECTIVES:To investigate the incidence, clinical significance, anatomical variation and physiology of non-saphenofemoral venous reflux (non-SF reflux) in the groin. DESIGN:Prospective study. MATERIALS:A total of 1072 vascular diagnostic workups in 680 patients with possible venous diseases to the legs were included. METHODS:Duplex scanning and air plethysmography. RESULTS:A total of 1022 legs had venous diseases. Of these, 101 (9.9%) had non-SF reflux in the groin. Such reflux occurred in recurrent varicose veins (RVV) in 16.3%, in primary varicose veins (PVV) in 6.1% and in deep venous thrombosis (DVT) in 8.0%. Two patterns of reflux were distinguished: epigastric reflux from lower abdominal wall veins (71 legs) and pudendal reflux from perineal and/or gluteal veins (30 legs). Pudendal reflux was almost exclusive to women and did not occur with DVT. If there was only non-SF reflux at the groin the venous filling indices (VFI) were close to normal (1.7+/-1.0 ml/s for RVV, 1.9+/-1.2 for PVV, 1.7+/-1.0 for DVT) and no active ulcers were observed. However, if non-SF reflux was associated with saphenofemoral or other reflux the VFIs (3.3+/-2.3 ml/s for RVV, 3.8+/-1.5 ml/s for PVV) were abnormal (p <0.05) and ulcers occurred in 11/32. CONCLUSION:Non-SF reflux in the groin is common. Such reflux may be missed at initial surgery and lead to recurrence of varicose veins. However, the venous physiological disturbance of such reflux is mild and it is not associated with ulcers unless combined with reflux at other sites in the leg.