Union of the greater tuberosity to the humeral shaft after hemiarthroplasty for acute fractures of the proximal humerus is a critical factor in the restoration of glenohumeral function. A retrospective review was undertaken to examine 23 consecutive patients who underwent hemiarthroplasty for the treatment of acute three- and four-part fractures of the proximal humerus. The study was conducted to examine the relationship between the position of the healed greater tuberosity and postoperative range of motion. The average age of the patients was 66.5 years. The average follow up was 3.8 years with a range of 24 to 108 months. Active range of motion was measured in forward elevation, external rotation, and internal rotation. Postoperative radiographs were examined to determine the position of the united greater tuberosity in relation to the top of the replaced humeral head. The tuberosity was fixed at an average of 15.4 mm below the top of the humeral head (range: 3 to 26 mm). A radiographic assessment of a control population of 50 normal proximal humeri demonstrated an average tuberosity position of 6.7 mm (range: 2 to 12 mm) below the superior aspect of the humeral head. Polynomial regression analysis demonstrated a polynomial relationship for active range of motion and tuberosity height. ANOVA testing demonstrated statistically significant differences in all ranges of motion. Active forward elevation for Group I (3 to 9 mm) was 88 degrees, Group 11 (10 to 16 mm) was 126 degrees, and Group III (17 to 26 mm) was 85 degrees (p = 0.04). Active external rotation for Group I was 19 degrees, Group II was 48 degrees, and Group III was 29 degrees (p = 0.01). Active internal rotation for Group I was to L2, Group II was to T10, and Group III was to L2 (p = 0.01). Although many factors affect the final ranges of motion in patients who undergo prosthetic replacement for acute proximal humeral fractures we believe that placement of the greater tuberosity 10 to 16 mm below the humeral head will assist in the maximum recovery of glenohumeral motion.