A 65-year-old man was suffering from recurrent manic psychosis accompanied by weight loss. He also had a history of pleural effusion, aspecific migratory non-deforming seronegative polyarthritis, sensorineural hearing loss and semicircular canal paresis. Whipple's disease (WD) had been diagnosed at the age of 63 years. On admission to hospital) he had weight loss, diarrhoea in combination with an organic brain syndrome, hemiparesis and ophthalmoplegia, including internuclear ophthalmoplegia (INO). A clinical diagnosis of central nervous system (CNS) WD was made. MRI revealed a thalamus lesion that halved in size during sulfamethoxazole-trimethoprim treatment. The organic brain syndrome and ophthalmoplegia diminished also, as did the cerebrospinal fluid (CSF) IgG level. A review of CNS WD is presented and implications for treatment are discussed.