Little is known about the fate of the donor site after the central 1/3 of the patellar tendon is harvested for anterior cruciate ligament reconstruction. This study evaluated the donor site in the patellar tendon at various times after a graft from the central 1/3 of the patellar tendon was harvested. Fourteen patients were studied with magnetic resonance images taken from 6 weeks to 2 years after anterior cruciate ligament reconstruction. Axial, sagittal, and coronal views of the patellar tendon were obtained. A second group of 8 patients who had previous anterior cruciate ligament reconstruction were returned to the operating room for subsequent procedures on the affected knee. These procedures were performed 2 to 24 months after the original reconstruction. An open biopsy was obtained from the donor site in the patellar tendon. On magnetic resonance images, the size of the defect and the intensity of the signal in the central 1/3 of the tendon decreased with time from surgery. At 2 years, the defect was indistinguishable from normal tendon. Histologically, the scar in the defect progressively matured with time, becoming nearly identical to normal tendon at 2 years.