Cardiac involvement in Whipple's disease has been a frequent autopsy finding but is rarely recognized clinically. We report here a patient, a 63-year-old man, in whom Whipple's disease was diagnosed in 1974, based on a seven-year history of arthralgia, one-year history of weight loss and steatorrhea, and diagnostic small bowel biopsy. Despite complete regression of all joint and bowel symptoms following a prolonged course of tetracycline therapy, the patient developed incapacitating congestive heart failure and signs of constrictive pericarditis, for which a thoracotomy and pericardectomy was performed. Histologic examination revealed fibrous pericarditis with mononuclear infiltrates, including PAS-positive histiocytes. The characteristic bacilliform bodies were identified by electron microscopy in the resected pericardium. This to our knowledge is the first such demonstration during life of Whipple's disease involving the heart.