Tibia valga has been described as a consequence of nondisplaced fractures of the proximal metaphysis of the tibia in children. There has been considerable speculation about the cause of this deformity. The present case is that of a child who developed a valgus deformity of her tibia after the fracture had healed in a normal position. The presence of growth arrest lines in the proximal metaphysis of the tibia demonstrates that the valgus deformity in this patient was caused by overgrowth of the medial portion of the proximal tibial epiphyseal plate.