The purpose of this study was to assess the diagnostic accuracy of transdeltoid palpation (the rent test) for the diagnosis of full thickness rotator cuff tear. Clinical and arthroscopic findings were documented prospectively for 109 consecutive patients undergoing shoulder arthroscopy by the senior author. A retrospective analysis was then performed on these data to assess the accuracy of transdeltoid palpation in the diagnosis of full thickness rotator cuff tear. Transdeltoid palpation was found to have a sensitivity of 95.7% and specificity of 96.8% for the diagnosis of full thickness rotator cuff tear. The positive and negative predictive values for transdeltoid palpation were 95.7% and 96.8%, respectively. Overall, the diagnostic accuracy of transdeltoid palpation was 96.3%. We conclude that transdeltoid palpation is highly accurate for the clinical diagnosis of full thickness rotator cuff tear.