A 43-year-old woman had since childhood suffered from progressive dementia. Gait ataxia and mild polyneuropathy were noted in the neurological examination. She also had painful xanthomas of the achilles tendons. A bilateral cataract operation had been performed during adolescence.An elevated concentration of cholestanol and a normal cholesterol level were found in the blood samples. The cerebral computed tomography revealed slight cerebral atrophy, predominantly affecting the cerebellum. Neurophysiological tests detected a sensory polyneuropathy in the legs. In addition the electroencephalogram showed a generalized slowing of electrical activity.Clinical findings and laboratory values indicated the diagnosis of a cerebrotendinous xanthomatosis. After initiation of a drug therapy, based on a combination of an HMG-CoA-reductase inhibitor (simvastatin 20 mg/day) and a bile acid, chenodeoxycholic acid (15 mg/kg/day), further progression of the disease was prevented.The diagnosis of cerebrotendinous xanthomatosis is easily made in patients presenting all clinical symptoms expected in the disease. However, up to 30% of the patients do not show severe xanthomas. Especially in early stages of the disease the diagnosis may be difficult. Treatment can be efficacious and should be started as early as possible to prevent irreversible damage, particularly in the nervous system.