From 1986-1992, a total of 21 ACL reconstructions were completed in 20 skeletally immature athletes with an average age of 13.7 years (range: 11.8-15.6 years). Fifteen patients underwent operative reconstruction with hamstring tendons with wide open physes and 6 patients with bone-patellar tendon-bone (BPTB). All grafts were anatomically placed through transphyseal bone tunnels in the femur and tibia. Nineteen of 20 patients (20 of 21 reconstructions) returned for follow-up at an average of 34 months (range: 17-89 months). All patients had reached skeletal maturity at follow-up. No patient had limb-length discrepancy >1 cm postoperatively. No change in tibiofemoral alignment was noted (average 4.5 versus 4.25, P=.69). Modified Lysholm score was 93/95, and 19 of 20 athletes returned to preinjury level sports activity. Ligament laxity side-to-side difference was <3 mm in 16 patients, 3-6 mm in 2 patients, and >6 mm in 2 patients. One patient developed recurrent symptomatic laxity and was lost to follow-up. Two late graft ruptures (1 hamstring and 1 BPTB graft) occurred after major reinjury during sports. In this group of patients, ACL reconstruction through bone tunnels successfully eliminated instability although the failure rate, including late graft ruptures, was higher than that usually reported for adults. No limb length or angular deformity developed as a result of the transphyseal tunnels.