This animal study evaluated the healing of supraspinatus tendon tears by use of a cartilage-derived morphogenetic protein 2 growth factor (CDMP-2) delivered to the repair. Forty-eight rats had bilateral, surgically created complete tears repaired by sutures with the growth factor introduced on one side. They were killed at 2, 3, 4, and 6 weeks, and the strength of the repairs was determined and histologic analysis performed. At 4 and 6 weeks, the CDMP-2-treated repairs were significantly stronger than the untreated repairs and histologic analysis showed more organized healing. The use of growth factors introduced at the time of rotator cuff repair might promote more rapid healing and subsequent, rapid patient rehabilitation.