Platelet-rich plasma (PRP) is a fraction of whole blood containing powerful growth factors and cytokines. Preclinical studies suggest PRP may be useful for tendon repair or regeneration. Clinical investigations have focused on the treatment of chronic lateral epicondylar tendinopathy and rotator cuff pathology. Multiple controlled studies support the use of PRP for chronic tennis elbow. Rotator cuff studies, however, have produced conflicting results based on PRP formulation, surgical technique, and size of tendon tear. This article explores the scientific rational for using PRP, its various formulations, and the emerging clinical data. Future potential applications are also explored.