Objectives: The effects of extreme behavioral lateralization (i.e., extreme handedness) on the epicondylar breadth are poorly understood. This study was conducted in order to determine the effects of high levels of right- and left-handedness on epicondyle of the humerus. Methods: Elbow width of 186 healthy male university students who completed their physical development (extreme left handed = 92, mean age = 18.67, SD = 0.61; extreme right handed = 94, mean age = 18.55, SD = 0.58) were measured with 0.01 mm sensitivity and Edinburgh Handedness Inventory was applied to determine the handedness of the individuals. Participants with scores of +100 were designated as extreme right-handers, and participants with scores of -100 were designed as extreme left-handers. Results: According to the findings, the degree of directional asymmetry was +1.22 (SD = 2.24) in the extreme right handed, whereas in extreme left handed -0.59 (SD = 1.74). The relative deviation percentage in the extreme right handed was 3.1% whereas 2.2% in the extreme left handed. Conclusions: It could be stated that extreme handedness has an influence on the asymmetry of epicondyle of the humerus; nevertheless, this effect is more significant in the extreme right handed. This is likely to result from the necessity for left-handed people to adapt themselves to the conditions of a dominantly right-handed world. Am. J. Hum. Biol. 2012. (C) 2012 Wiley Periodicals, Inc.