During 5,050 stripping operations for varicose veins, three noticeable deviations from the normal anatomy were encountered. In two patients (0.04%) the long saphenous vein entered the femoral vein completely separate from its branches, which joined to form a common trunk before emptying into the femoral vein. In one patient (0.02%), the femoral vein and artery were transposed in the region of the fossa ovalis. In one patient (0.02%), a long saphenous artery was encountered. It arose from the femoral artery just proximal to the origin of the deep femoral artery and accompanied the long saphenous vein along the medial aspect of the upper thigh. In some patients, a large venous cluster overlying the fossa ovalis was encountered, usually the result of a congenital venous anomaly. Surgical problems can be minimized if the possibility of these congenital anomalies is always considered.