Correct placement of the tibial and femoral tunnels is critical to the success of any anterior cruciate ligament reconstruction. Three characteristics of correctly placed tunnels are reviewed, including prevention of graft impingement against the intercondylar roof during extension, prevention of graft impingement against the posterior cruciate ligament during flexion, and replication of the tension pattern of the intact anterior cruciate ligament. The transtibial technique, in which the tibial tunnel is positioned and drilled first and then the femoral tunnel is positioned and drilled through the tibial tunnel, is the focus of this paper. The importance of correctly placing the tibial tunnel in the sagittal and coronal planes is emphasized for two reasons: (1) the placement of the tibial tunnel in the sagittal plane determines whether there is roof impingement, and (2) the placement of the tibial tunnel in the coronal plane controls the placement of the femoral tunnel, which determines whether there is posterior cruciate ligament impingement and high graft tension. The development and step-by-step use of a tibial and femoral guide system designed for use with the transtibial technique is presented. The indications, contraindications, and clinical results using this guide system and the shortcomings of the point-and-shoot and posterior cruciate ligament referencing guides are discussed.