We describe the histologic findings of biopsies performed on specimens from 14 patients with nonsteroidal antiinflammatory drug (NSAID) associated colitis. Thirteen patients had endoscopially patchy colitis with small erosions in different parts of the colon. One patient had diffuse colitis extending from the rectum to the midtransverse colon. Histologically, 8 patients had a mixed inflammatory infiltrate, 4 had predominantly neutrophilic inflammation, and 2 had predominantly lymphocytic inflammation. Seven patients had erosions. Eight patients had crypt architectural disarray, but none had crypt architectural distortion or granulomas. The histology of NSAID-associated colitis is similar in our experience to that of Crohn disease and infectious-type colitis. It shares no features with ulcerative colitis. Given the widespread use of NSAIDs, pathologists should consider NSAID-associated colitis along with Crohn disease and infectious-type colitis in the histologic differential diagnosis of focal active colitis.