76 patients with a large full-thickness posterosuperior rotator cuff tear were randomized to receive arthroscopic rotator cuff repair with or without a platelet-leukocyte membrane. After a follow up of a mean of 13 months, the two groups were assessed based on Constant scores, the integrity of the repair, and Simple Shoulder Test (SST) scores. The two groups did not differ significantly in their change in Constant or SST scores. However, the patients who received the membrane demonstrated significantly greater repair integrity at follow up than those who did not receive the membrane. However, it should be noted that patients receiving the membrane were significantly younger than patient who did not receive the membrane.