During the past two decades the vascular anatomy of the trapezius muscle has been the subject of several anatomic studies. The anatomy of the trapezius is variable and confusing, and this anatomic variability seems to be the basis for sometimes unpredictable clinical results of the trapezius muscle flap. The purpose of the present study was to provide a careful overview of the intra- and extramuscular anatomy of the trapezius. In a series of 10 fresh and 10 preserved cadaveric studies, the intra- and extramuscular anatomy of the trapezius as well as the intramuscular neurovascular anatomy were studied. It was found that there are two main patterns of vascular supply to the trapezius, and that the muscle is principally supplied by three vascular sources: the transverse cervical artery, the dorsal scapular artery, and the posterior intercostal arterial branches. Although this study of the vascular anatomy of the trapezius helps to clarify the cause of the occasional loss or partial loss of the trapezius muscle, it does not provide a means of preventing partial flap loss.