Crossover reflux routes were detected in 25 of 54 (46%) legs with lateral and in 11 of 103 (11%) legs with medial ulceration (χ2 44.34; P<.001). In venous ulcer patients, an extended examination (CEAP classification) and a special duplex technique ("sourcing") are recommended to identify the specific route responsible for the venous reflux. This seems essential for planning a rational treatment of venous reflux ulcers.