Whipple's disease is a chronic systemic infection that is due to the bacterial agent Tropheryma whipplei and can be cured by appropriate antibiotic therapy. The typical patient is a middle-aged man. Rheumatologists are in a prime position to handle Whipple's disease. The classical presentation combines weight loss and diarrhea, preceded in three-quarters of patients by a distinctive pattern of joint manifestations that run an intermittent course, at least initially. The mean time from joint symptom onset to the diagnosis of Whipple's disease is 6 years. Either oligoarthritis or chronic polyarthritis with negative tests for rheumatoid factors (RFs) develops. If the diagnosis is missed, progression to chronic septic destructive polyarthritis may occur. Spondyloarthritis has also been reported, as well as a few cases of diskitis or, even more rarely, of hypertrophic osteoarthropathy. In most patients with the classical form of Whipple's disease, periodic acid-Schiff (PAS) staining of duodenal and jejunal biopsies shows macrophagic inclusions that contain bacteria. However, the involvement of the bowel may be undetectable clinically or, less often, histologically, and even PCR testing of bowel biopsies may be negative. Therefore, when nothing points to bowel disease, rheumatologists should consider T. whipplei infection in middle-aged men with unexplained intermittent oligoarthritis. PCR testing allows the detection of T. whipplei genetic material in joint fluid, saliva, and feces. This test is now a first-line diagnostic investigation, although T. whipplei is a rare cause of unexplained RF-negative oligoarthritis or polyarthritis in males. PCR testing can provide an early diagnosis before the development of severe systemic complications, which are still fatal in some cases.