The cross-sectional area of the 10-mm wide patellar tendon graft was measured in 50 consecutive patients (31 males and 19 females) who underwent isolated anterior cruciate ligament (ACL) reconstruction and the relationship between the graft size and various factors such as physical characteristics was assessed. The effect of cross-sectional area of the implanted graft on postoperative stability of the reconstructed knee also was examined. Mean patient age at surgery was 22.3 years (range: 14-40 years). The cross-sectional area was measured using an instrumented area micrometer intraoperatively, and correlations between the measured value and various factors such as age, gender, height, body weight, and bony geometry were examined. Follow-up was performed 24 months postoperatively. The average cross-sectional graft area was 33.4 mm2. The measured cross-sectional area was larger in male patients and correlated with physical characteristics such as height, body weight, and femoral condyle width. No significant correlation between the size of the graft and postoperative stability was observed.