This paper presents a case of Crohn's disease with associated small bowel adenocarcinoma. A polypoid area of gastric metaplasia was present and showed both fundic and pyloric features, the latter showing increasingly severe dysplasia and infiltrating adenocarcinoma containing many enterochromaffin cells, in which serotonin was demonstrated. At foci of granulomatous inflammation one observed a well differentiated sulfomucin secreting adenocarcinoma. Away from the metaplastic or inflammatory lesions there arose both a poorly and well differentiated sialomucin secreting adenocarcinoma. Multiple microfoci of adenocarcinoma and dysplastic changes of the ileal epithelium were present in the absence of any gross abnormality.