Whipple's disease is a chronic, multisystemic, curable, bacterial infection that usually affects middle-aged men. It has a wide range of clinical manifestations. In the historical presentation, weight loss and diarrhoea are the most common symptoms and are preceded in three-quarters of cases by arthritis for a mean of six years. Long-term, unexplained, seronegative oligoarthritis or polyarthritis of large joints with a palindromic or relapsing course is typical. In most patients, periodic acid-Schiff staining of proximal small bowel biopsy specimens reveals inclusions within the macrophages, corresponding to bacterial structures. However, patients may have no gastrointestinal symptoms, negative jejunum biopsy results and even negative PCR tests. Even in the absence of gastrointestinal symptoms, Whipple's disease should be considered in case of negative blood culture endocarditis, unexplained central neurological manifestations or unexplained arthritis. Identification of the causative bacterium, Tropheryma whipplei, has led to the development of PCR as a diagnostic tool, particularly useful in patients in the early stages of the disease or with atypical disease. The recent cultivation of T. whipplei and the complete sequencing of its genome should improve our understanding and treatment of the disease. The future development of an assay for detection of specific antibodies in the serum and generalization of the immunohistochemical detection of antigenic bacterial structures may allow earlier diagnosis, thereby preventing the development of the severe late systemic and sometimes fatal forms of the disease.