A rare variant of the origin of the median and the musculocutaneous nerves is reported. The lateral fasciculus of the brachial plexus pierced the coracobrachialis muscle, gave muscular branches to the coracobrachialis and biceps brachii, and then divided at the middle of the upper arm in two terminal branches. The first one trifurcated, giving two branches for the brachialis muscle, and the lateral antebrachial cutaneous nerve; the second one corresponded to the lateral root of the median nerve. This lateral root joined the medial root, and gave the proper median nerve. No accurate description of a similar case has been found in the literature. The peculiarity of this observation leads us to propound a new classification, in five types, of the variations of these two nerves reported in the literature.