An unusual case of chronic ulcerative colitis, is presented in which an atypical carcinoid tumor was seen. Many areas of the mucosa showed glandular changes of chronic injury and dysplasia, and in these areas, argyrophilic cell hyperplasia was identified. Data is presented describing the evolution of argyrophilic cell hyperplasia as a reaction to injury, the evolution of carcinoid tumors in argyrophilic cell hyperplasia, and the relationship of the proliferating argyrophilic cells to the proliferating glandular cells in ulcerative colitis.