Many cases of central nervous system (CNS) Whipple's disease are not diagnosed until postmortem. Few reviews of CNS Whipple's disease have delineated the frequencies of abnormalities on neurological examination, cerebrospinal fluid studies, neuroimaging, and intestinal biopsy studies. Guidelines for diagnosis and treatment have not been proposed. In this review we present 3 new cases of CNS Whipple's disease and summarize the literature to determine the frequencies of neurological signs and abnormalities on diagnostic testing. We propose guidelines for diagnostic screening, selection for biopsy, and treatment. Review of the 84 cases of CNS Whipple's disease (81 in the literature, 3 new) revealed that 80% of the patients had systemic signs. Cognitive changes were frequent (71%), and 47% with cognitive changes also had psychiatric signs. Oculomasticatory myorhythmia and oculo-facial-skeletal myorhythmia, pathognomic for CNS Whipple's disease, were present in 20% of patients, and were always accompanied by a supranuclear vertical gaze palsy. Tissue biopsy was a sensitive technique; 89% of those who had biopsies had positive biopsy results. Diagnosis and treatment of definite CNS Whipple's disease should be based on the presence of pathognomic signs (oculomasticatory myorhythmia or oculo-facial-skeletal myorhythmia) or positive biopsy or polymerase chain reaction results. Possible CNS Whipple's disease should be diagnosed in the setting of unexplained systemic symptoms and neurological signs (supranuclear vertical gaze palsy, rhythmic myoclonus, dementia with psychiatric symptoms, or hypothalamic manifestations). Those with possible CNS Whipple's diseae should undergo small-bowel biopsy.