SUMMARY: The median nerve is responsible for the innervation of the muscles of the superficial layer of the anterior compartment of the forearm, it originates along its course in the arm and forearm, branches to these muscles. Some branches originated from common trunks (Ct). We studied 30 upper limbs of Brazilian adults corpses, fixed in 10 % formaldehyde in order to obtain an anatomical and biometric description of the origin and distribution of the branches of the median nerve in the superficial muscles of the forearm: pronator teres (Pt), palmaris longus (PL), flexor carpi radialis (FCR), flexor digitorum superficialis (FDS) and classify these branches (Br) according to their origin. We performed dissections and recorded origins in relation to the biepicondilar line (BEL). With the results we obtained a classification of the branches to the muscles of the superficial layer of the anterior compartment in 4 patterns (I, II, III, IV; the I classified in IA and IB), including the origin of anterior interosseous nerve (AIN). In the pattern IA (29 %), branches originated from proximal to distal in the following sequence: CtPT, PL, FCR, AIN, Br1FDS, Br2FDS; in pattern IB (41 %) showed CtPt, TcFCR and PL, AIN, Br1FDS, Br2FDS; in pattern II (4 %) was CtPt and FCR, PL, AIN, Br1FDS, Br2FDS, Br3FDS; in pattern III (11 %) it was CtPt, Ct FCR and PL, AIN, Br1FDS, Br2FDS, Br3FDS and in pattern IV (15 %) was Br1Pt, Br2Pt, CtFCR and PL, Br1FDS, AIN, Br2FDS. In type pattern IB, the first muscle to receive branches from the median nerve in the forearm was the PT, which in 53 % of cases originated from a common trunk. The PL was the second to be innervated, leaving third place to FCR, which 50 % were supplied by a common trunk. The latest to be innervated muscle was the FDS, which received two branches in 57 % of cases. The results are a contribution to the knowledge of the innervation of the muscles of the super- ficial layer of the anterior compartment of the forearm.
KEY WORDS: Anatomy; Forearm; Median nerve; Motor branches.