A rare complication of osteoid-osteoma is localized overgrowth and/or deformity of bone. Six of 64 cases reviewed had this growth disturbance. All patients developing deformities had their onset of symptoms before 5 years of age. Not one of the patients had limb equalization or correction of the deformity after removal of the osteoid-osteoma. The longest follow-up was 8 years. Speculations on the underlying cause for this form of growth abnormality, and the incidence in infants and very young children suggests that immediate surgical treatment is the best course of action.