 One aim of the present study is to better understand the natural history of IXT. Available reports on the natural history of IXT disagree on the progression of the disease. A 1966 study by von Noorden cited in von Noorden and Campos found that over an average of 3.5 years of follow-up, 75 of 51 patients showed signs of IXT progression, 9 showed no change, and 16 improved without therapy. A 1968 retrospective study by Hiles et al found that after a minimum of 6 years follow up with observation and nonsurgical treatment, 81 of 48 patients showed no change in angle of deviation. The results of more recent retrospective studies show some reporting that the majority of cases improve over time, others reporting that most cases remain stable, and still others reporting that most cases deteriorate. It is therefore unclear what proportion of patients, if left untreated, is likely to deteriorate, improve, or remain stable over time. Natural history data acquired during this study will help determine not only what proportion of patients change over time, but whether there are associated prognostic indicators of deterioration or improvement. Such data will not only enable better identification of those patients with IXT likely to benefit from treatment and those for whom treatment is likely to be unnecessary, but will also improve the quality of medical advice to parents regarding the likely progression of the disease, thus alleviating anxiety. 