Twenty-two patients with malignant carcinoid syndrome were evaluated with CT, the largest series to date. A mass representing the primary tumor or local adenopathy was identified in four patients, appearing as a homogeneous mass involving mesentery and bowel. In two other patients the primary was not identifiable by barium series, angiography, CT, or laparotomy. In the remaining 16 patients who were scanned after resection of the primary four had mesenteric thickening and five had adenopathy. Malignant ascites was present in seven of 21 patients. All hepatic metastases were hypodense on the precontrast study. The effect of contrast administration on lesion detectability was variable, obscuring at least one or more metastases in eight of 21 scans. We recommend noncontrast scans of the liver in patients in whom the number and size of metastases are critical to therapy.