The pathogenesis of adenomas in adenomatous polyposis of the gastrointestinal tract (familial polyposis coli, FPC) is not completely known. The morphologic features of the dysplastic epithelium and the morphogenesis of adenomas in FPC have been well described. Studies of the precursors to adenomatous epithelium have identified histopathologic, ultrastructural, and epithelial proliferative abnormalities in grossly normal colonic mucosa of FPC patients. The role of the intraluminal environment and the mechanisms of its interaction with the mucosa appear to be important areas for research directed at the pathogenesis of adenomas in FPC, due to the implications for therapy.