Purpose: the purpose of this study was to evaluate defect width of patellar tendon after harvest for anterior cruciate ligament reconstruction. Materials and methods: we performed MRI at various time interval after graft harvest (2-96 months) on 28 patients who had had reconstruction of the anterior cruciate ligament using mid-third patellar tendon. T1 and T2 weighted axial images were obtained to assess donor site defect of the patellar tendon. Measurement of the defect width was performed at the level of menisci on the axial images. The patients were divided into two groups according to the time interval between operation and imaging. The defect width of patients with short time interval (2-12 months) was compared to the defect width of patients with long time interval (12-96 months). Results: the average defect width of patients with short time interval was 6.4 mm and it was 2.2 rum for the patients with long time interval. Decreased defect width was obtained from MRI images in the patients with long time interval. Closed donor site defect was detected in I out of 14 patients with short time interval and 6 out of 14 patients with long time interval. Discussion and conclusion: these results show that there is no complete closure of donor site defect up to I year. However, it seems to be nearly complete Closure of patellar tendon defect in the long time period. (C) 2003 Elsevier Ireland Ltd. All rights reserved.