Rectal biopsies of sigmoidoscopically normal mucosa from 99 patients with Crohn's disease of the ileum, colon, or both were studied histologically, with particular reference to the presence of granulomas. Among the 14 cases of granulomas, some were of the usual sarcoid type and could easily be detected. Other microgranulomas were less well defined and were found only by mid- or high-power microscopic screening of serial sections. The morphologic characteristics, the relationship to ordinary Crohn's-disease granulomas and the possible significance of microgranulomas are discussed.