In twenty-nine specimens from fresh cadavera, we performed an anatomical study of the arteries of the humeral head to determine their intraosseous distributions. A radiopaque suspension was injected into the anterior circumflex, posterior circumflex, suprascapular, thoracoacromial, or subscapular artery and then the specimens were dissected and were analyzed macroscopically, and radiographs were made in three mutually perpendicular projections. In addition, sixteen of the specimens were cut into four-millimeter slices and were studied microradiographically. The humeral head was shown to have been perfused by the anterolateral ascending branch of the anterior circumflex artery in all specimens. That vessel ran parallel to the lateral aspect of the tendon of the long head of the biceps and entered the humeral head where the proximal end of the intertubercular groove met the greater tuberosity. When the intraosseous (terminal) part of the anterolateral branch, the so-called arcuate artery, had been perfused, almost the entire epiphysis was radiopaque. The posterior circumflex artery vascularized only the posterior portion of the greater tuberosity and a small posteroinferior part of the head. Anastomoses between the different arteries were abundant, but vascularization of all of the humeral head was possible only through the anterolateral branch of the anterior circumflex artery.