We describe a 70-year-old woman who presented with watery diarrhea and was found to have gastric and colonic polyposis, cutaneous hyperpigmentation, alopecia and onychodystrophy (Cronkhite-Canada syndrome). Histology of a polyp from the stomach showed features of juvenile or retention type (hamartomatous) polyp. One colonic polyp revealed features of tubular adenoma, with moderate dysplasia. Another large pedunculated colonic polyp showed a tubulovillous adenoma with a focus of well-differentiated adenocarcinoma confined to the submucosa of the stalk. Adenomatous and carcinomatous epithelial changes can occur in Cronkhite-Canada syndrome.