Cerebrotendinous xanthomatosis (CTX) is a rare lipid storage disorder due to an autosomal-recessive inherited defect of the hepatic mitochondrial steroid 26-hydroxylase. The resultant reduced biosynthesis of cholic and especially chenodeoxycholic acid and the increased production and accumulation of cholestanol and cholesterol in most tissues is described and pathogenetic aspects as well as typical pathological findings are discussed. In the light of three personal observations the clinical symptoms and the results of auxiliary investigations are discussed and compared with the literature. The suspected diagnosis of CTX may be confirmed by demonstration of a pathologically elevated concentration of cholestanol or biliary alcohols in serum and urine respectively. The chronically progressive neurologic deficit can be halted or is in some cases partially reversible by treatment with chenodeoxycholic acid. Therefore, early diagnosis is mandatory and CTX should be considered in every patient presenting with intellectual impairment, spastic-ataxic signs, juvenile cataracts and tendon xanthomas.