The etiology of genu varum in achondroplasia is the subject of much speculation. The purpose of the current study was to investigate the association between fibular overgrowth and genu varum in achondroplasia. A retrospective analysis was performed on the long-leg radiographs of 48 pediatric patients with achondroplasia. All patients were skeletally immature, and the average age was 7.7 years (range, 3-16 years). Boys were significantly more likely to have varus mechanical tibiofemoral angles than girls (Fisher exact test, P=0.038 for the right leg and P=0.008 for the left leg). The distance from the proximal and distal fibula to the proximal tibia knee and ankle joint orientation lines, respectively, was not associated with the alignment of the lower extremity. We conclude that fibular overgrowth does not correlate with the severity of genu varum.