Abnormal musculotendinous distal extension of the peroneus brevis has been implicated as a possible cause of peroneus brevis tendon tears. We investigated this relationship in 58 (46 male) fresh human cadavers. Torn lesions were classified according to Sobel et al. Musculotendinous distal extension of the peroneus brevis was measured in each ankle as the vertical distance from the musculotendinous junction of the peroneus brevis to the tip of the fibula. Tendons with and without tears were compared by sex, age at death, height, musculotendinous distal extension of the peroneus brevis, the common sheath bifurcation-fibular tip distance, the peroneus brevis and longus width at the musculotendinous junction, fibular groove depth, peroneal tubercle height, superior-inferior peroneal retinaculum wideness, and the presence of the peroneus quartus or an accessory peroneal muscle. Of 115 evaluable tendons, 15 (13%) had tears. All came from men. The average distance from the musculotendinous junction to the tip of the fibula was 27.0 mm in tendons with tears and 16.4 mm in tendons without (P=.04) Male sex (P=.03), age at death (P=.03), height (P=.04), and fibular groove depth (P=.003) were also related to the presence of tears. Our results do not support a relationship between abnormal musculotendinous distal extension of the peroneus brevis and peroneus brevis tendon tears; rather, proximal extension of the peroneus brevis musculotendinous junction may be related to peroneus brevis tendon tears. (C) 2010 by the American College of Foot and Ankle Surgeons. All rights reserved.