Objectives: Long head biceps (LHB) tenodesis can be performed open or arthroscopically and can be positioned in a suprapectoral or subpectoral position. Suprapectoral tenodesis is easier to accomplish arthroscopically, whereas the subpectoral tenodesis is performed as an open procedure with a longitudinal skin incision at the lower border of the pectoralis major muscle. Numerous studies have investigated these tenodesis techniques, comparing them to tenotomy, and comparing fixation methods between techniques, however, no study has compared the actual postoperative clinical location of suprapectoral and subpectoral LHB tenodesis. The goal of this study is to compare the radiographic location of clinically-performed arthroscopic suprapectoral and open subpectoral biceps tenodesis. Methods: Study Design: Retrospective study. The charts of all patients who underwent arthroscopic or open biceps tenodesis in the past 5 years were reviewed. We routinely obtained post-operative x-rays in these patients and those with available x-rays and complete preoperative information were included in the study. Analysis: The location of all tenodesis sites were measured on x-rays as the distance from the top of the humeral head. Means and standard deviations were calculated and compared using Student’s t-test. Outliers were identified as patients with tenodesis locations greater than one standard deviation from the mean. Preoperative clinical characteristics of these patients were compared to the remaining tenodesis patients using Student’s t test for continuous variables and chi square tests for categorical variables. Results: We identified 158 patients who met inclusion criteria, which included 66 open subpectoral tenodeses and 92 arthroscopic tenodeses. Power analysis determined that 47 patients in each group (94 total) was the minimum number necessary to determine an 8mm difference between groups. The average distance from the top of the humerus (TDH) in the arthroscopic suprapectoral group was 4.89 +/- 0.8 cm, and in the open subpectoral group, 7.52 +/- 1.2 cm. (Fig 1) This difference is statistically significant (p<0.0001). 12 (18%) distal outliers (more than one standard deviation distal) were found in the open subpectoral group. 11 (12%) proximal outliers were found in the arthroscopic suprapectoral group. Analysis determined that increased BMI and male gender were significant predictors for distal placement of an open tenodesis. No significant predictors of proximal arthroscopic tenodesis were found. Published cadaveric data localizes the proximal edge of the pectoralis major tendon to be 5.6 cm distal to the top of the humerus. Our data indicates that arthroscopic suprapectoral tenodesis results in a tenodesis location very near (within 0.7cm on average) the proximal edge of pectoralis major tendon. Open subpectoral technique results in a truly subpectoral location, 1.9 cm distal to the proximal edge of the tendon, likely representing the clinical height of the pectoralis major tendon at the bicipital groove. Conclusion: Arthroscopic suprapectoral and open subpectoral techniques result in significantly different locations of biceps tenodesis. Surgeons experienced in these techniques can expect, on average, to localize their tenodesis just proximal to the pectoralis major tendon using an arthroscopic technique and just distal to the tendon using an open subpectoral technique. The clinical significance of these findings is currently being studied.