The purposes of this study were to determine the frequency and characteristics of calcification and fibrosis in mesenteric carcinoid tumor as seen on CT scans and to evaluate their possible role in diagnosis. The CT findings in 29 cases of proved mesenteric carcinoid tumor were analyzed retrospectively. Tumors were assessed for size, margin, density, radiating strands, calcification, and associated thickening of the small-bowel wall. Matching histologic sections were available for 21 of the cases. They were reviewed independently for histologic pattern, degree of fibrosis, degree of infiltration along neurovascular bundles, necrosis, lymph node architecture, and calcification or ossification within the mass. CT and pathologic findings were then assessed for possible relationships. Calcification was detected by CT in 70% (21 of 30) of mesenteric masses. Three patterns of calcification were noted: small, stippled calcification (n = 11); coarse, dense calcification (n = 7); and diffuse calcification (n = 3). All calcification was localized within areas of poorly cellular mature fibrous tissue. The degree of radiating strands detected by CT tended to increase with the degree of fibrosis seen histopathologically (p = .06). Calcification in mesenteric carcinoid tumors was observed by CT in most cases of this series. The triad of a calcified mesenteric mass, radiating strands, and adjacent bowel-wall thickening should be considered highly suggestive of carcinoid tumor.