Over an 18-year period we have diagnosed nodular lymphoid polyposis of the intestinal tract in 6 patients. The site of the polyposis, which was due to prominent lymphoid hyperplasia, was ileal (3), colonic (2), and rectal (1). The diagnosis was made following complications arising from the polyps, which included recurrent intussusception (2), rectal prolapse (1), intestinal or pseudointestinal obstruction (2), and rectal bleeding (1). Immunoglobulin staining was performed on all the bowel specimens and in every case secretory IgA was present on the mucosal surfaces and IgG and IgA were seen in the lamina propria, thus excluding immunodeficiency in these patients. Viral studies were performed in 3 patients and all were positive. In one patient Echovirus II was seen in tissue homogenate from a mesenteric lymph node and in another, adenovirus type II was cultured from lymphoid polyps of the rectum. A further patient had positive serological tests for adenovirus. Thus it appears that nodular lymphoid hyperplasia is part of the generalized lymphoid hyperplasia associated with viral infections in infancy and childhood. Immunodeficiency states as a cause of the lymphoid hyperplasia should always be excluded by estimation of serum immunoglobulins.