Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder of bile acid synthesis which can be clinically diagnosed and specifically treated. It is an underdiagnosed disorder worldwide.Here,we describe two women who were diagnosed with CTX during their forties after symptoms had already developed 15 years earlier. Both patients showed gait ataxia, spastic paraparesis, polyneuropathy, bilateral premature cataracts, tendon xanthomas, and cognitive deficits. One of the patients had also chronic diarrhea. The deficiency of the mitochondrial enzyme sterol 27-hydroxylase results in a virtual absence of chenodeoxycholic acid. This leads to excessive production of cholestanol and cholesterol and accumulation of these sterols in many tissues, especially the eye lens, central nervous system,and tendons. The determination of a high cholestanol serum level allows the diagnosis,which can be confirmed through genetic analysis. Early diagnosis of CTX is important, since an effective therapy is available. Long-term therapy with chenodeoxycholic acid is effective for CTX, mainly in prevention of further deterioration.