The rationale and history of the CDCA therapy in CTX are reported in the chapter on the history of this disease in this book. Here we describe our findings in the Italian cohort of patients with a long-duration therapy of chenodeoxycholic acid. In particular, we describe stabilization of the clinical deterioration, improvement of serum cholestanol levels associated with a decrease of 7-α-hydroxycholesterol, and less prominent of lathosterol and sitosterol, while 24- and 27-hydroxycholesterol were unchanged, improvement of nerve conduction velocities, improvements of vitamin D absorption, and reduced bone demineralization, with very few side effects. In our experience, early treatment is coincident with a better prognosis. We also report very early therapy in a child with neonatal biochemical and molecular CTX diagnosis in which CDCA therapy, with more than 14 years follow-up, resulted in the absence of any clinical presentation of the main symptoms of CTX as has been reported by other groups.