An alternative treatment is presented for late-onset Blount disease in a 14-year-old boy. The technique consists of asymmetric physeal distraction of the proximal tibial growth plate by using a modified Wagner fixator-distractor device that allows progressive angular correction. The patient had a 23 degrees varus deviation of the left tibia, and no physeal bone bridges were detected. Once the fixator was assembled, distraction started 24 h after surgery at a rate of 1.5 mm/day (2 x 0.75). Complete correction was achieved in 25 days. No osteotomy of the fibula was required. The Wagner device was removed in the outpatient clinic 10 weeks postoperatively. After a 4-year follow-up, there was no loss of correction, showing a satisfactory alignment of the operated-on lower extremity. As compared with acute conventional osteotomies, asymmetric physeal distraction entails several advantages for treatment of Blount disease such as less invasive surgery, progressive and adjustable correction taking place at the apex of the deformity, and the possibility of bone lengthening if needed. Furthermore, physeal distraction does not require a second surgical step for bonegraft harvesting or for removal of the internal fixation.