We analyzed a consecutive series of 71 small bowel adenocarcinomas identified over an 8-year period for DNA mismatch repair (MMR) protein expression to (1) compare the clinicopathologic features of small bowel adenocarcinoma stratified into MMR-deficient (MMRD) and MMR-proficient (MMRP) groups and (2) examine the patterns of MMR protein expression in small bowel adenocarcinoma compared with colorectal carcinoma.