Partial-thickness tears of the rotator cuff have been diagnosed with increased frequency because of a heightened awareness of the condition by clinicians and improved diagnostic methods. Research into the causes, natural history, and optimal treatment of this condition lags behind that of full-thickness tears. However, despite the limitations in the existing literature, there has emerged a consensus among shoulder experts that partial-thickness rotator cuff tears should be aggressively treated in the active athlete because of the unfavorable natural history of these lesions and success of accepted surgical algorithms. This review will provide an overview of the theories regarding the origins of partial-thickness rotator cuff tears, discuss the relative accuracy of accepted diagnostic techniques, and summarize the indications and methods of operative repair with an emphasis on the results of various treatment approaches.