OBJECTIVE To determine whether the preoperative magnetic resonance imaging (MRI) cross-sectional area (CSA) of the hamstring tendons can predict intraoperative bundle diameters during double-bundle anterior cruciate ligament reconstruction. METHODS A prospective study of 34 patients undergoing anterior cruciate ligament reconstruction with hamstring autografts was performed. CSAs of independent and combined hamstring tendon diameters were correlated to preoperative magnetic resonance images. RESULTS Intraoperative tendon diameter measurement positively correlated with preoperative MRI tendon CSA measurement for gracilis (P = .0006), semitendinosus (P = .001), and final graft size (P = .001). Double-stranded gracilis grafts greater than or equal to 5 mm in diameter had a mean preoperative MRI gracilis CSA of 9.98 mm(2) compared with a mean of 7.76 mm(2) for grafts less than 5 mm (P = .002). Double-stranded semitendinosus grafts greater than or equal to 6 mm had a mean preoperative MRI tendon CSA of 17.33 mm(2) compared with 14.80 mm(2) for grafts less than 6 mm (P = .02). Final grafts of diameter greater than or equal to 7 mm had a mean preoperative MRI total tendon CSA of 26.54 mm(2) compared with 22.22 mm(2) for grafts under 7 mm (P = .06). CONCLUSIONS Preoperative MRI is a clinically useful tool to assess hamstring tendon graft diameter. We recommend preoperative CSA threshold values of 10 mm(2) and 17 mm(2) for the gracilis and semitendinosus tendons, respectively, to reliably predict the potential for a double-bundle anterior cruciate ligament reconstruction. METHODS Level IV, therapeutic case series.