There are relatively few reports that detail the types of intestinal adenocarcinoma complicating Crohn's disease and examine associated epithelial dysplasia. We determined the prevalence, grade, and type of dysplasia found adjacent to and distant from Crohn's-related adenocarcinomas. Thirty cases of resected Crohn's-related adenocarcinoma were reviewed, and histologic type, degree of differentiation, TNM stage, and the presence or absence, grade, and location of dysplasia were recorded. Most of the patients were male (70%). The median ages at diagnosis of Crohn's disease and adenocarcinoma were 34 and 49 years, respectively. The extent of Crohn's disease included ileocolitis in 21 patients, only colonic disease in six, and only small bowel disease in three. In most cases (67%), carcinoma was found incidentally at surgery. All carcinomas arose in areas involved by Crohn's disease. Eight (27%) adenocarcinomas arose in the small bowel, and 22 (73%) arose in the colon, including two in out-of-circuit rectums. Most carcinomas (63%) were poorly differentiated. Dysplasia was found adjacent to the carcinoma in 26 (87%) cases. Of the colorectal carcinomas, 19 (86%) had adjacent dysplasia, and nine (41%) had distant dysplasia. In conclusion, most cases of Crohn's-related intestinal adenocarcinoma have dysplasia in adjacent mucosa, and 41% of those arising in the colorectum have distant dysplasia, supporting a dysplasia-carcinoma sequence in Crohn's disease.