Whipple's disease is characterized by malabsorption, weight loss, diarrhoea and abdominal pain, often preceded by a long period of migrating arthralgias. Instead of the intestine the heart, brain, eyes, lungs or blood vessels may be affected. Whipple's disease is caused by Tropheryma whippelii, a bacillus found inside phagocytes. A specific defect in the immune system of the host appears to play a part. The diagnosis is based on microscopic examination of periodic-acid-Schiff(PAS)-stained slides and on polymerase chain reaction (PCR) analysis of affected tissue. Recently a method for culturing T. whippelii was described. Prolonged treatment with cotrimoxazole, preceded or not by two weeks of penicillin and streptomycin, often cures the disease, but relapses do occur.