The anatomical variations of the biceps brachii muscle in relation to the number of supernumerary or accessory bellies may have important incidence in clinical and radiological diagnoses, as well as in surgical procedures. The absence of an appropriate classification for the variations that the biceps brachii muscle can present and the findings of the present study, allowed the authors to present a classification proposal based on the number of accessory bellies and their origin. The study aimed to determine with which frequency the variations in the number of accessory bellies of the biceps brachii muscle are present, and to propose a classification for these variations. In the cross- sectional, descriptive study 90 arms of 46 Colombian cadavers were analyzed. A high frequency (19.6 %) in the variations of the muscle was found, 4.3 % bilaterally and 15.2 % unilaterally. In the 11 arms (12.2 %) that presented the variation, the presence of only one accessory belly was the highest frequency (81.8 %), being the most frequent origin for them the one classified by the authors as 3b, 3 for the inferomedial situation and b for the interval between the insertion of the coracobrachii muscle and the origin of the brachii muscle. Because the classification proposed is very detailed, its use is recommended whenever cases of biceps brachii muscle variations are reported. In the cadavers of the Colombian population studied, a high frequency was found for the presence of supernumerary or accessory heads of this muscle, which deserves to be known by medical professionals.
KEY WORDS: Anatomic variation; Biceps brachii muscle; Accessory bellies; Arms; Cadaver.