Few have examined the distribution of the radial nerve branch to brachialis, generally believed to be motor, within the muscle. We examined the right brachialis muscles of six dissecting room cadavers and found that four received a supply from the radial nerve. The radial nerve branch(es) supplied the inferolateral region of the muscle and was overlapped proximodistally and mediolaterally by the intramuscular branches of the musculocutaneous nerve, which lay on a more superficial plane. The results have implications for the anterolateral approach to the humerus for orthopedic surgery. Anterior splitting of the muscle will almost certainly damage the most lateral branches of the musculocutaneous nerve.