Recent data suggest that functional receptors (R) for vasoactive intestinal peptide (VIP) are expressed on various tumor cells. The high-level expression of VIPR on tumor cells provided the basis for the successful use of 123I-labeled VIP for the in vivo localization of intestinal adenocarcinomas and endocrine tumors. We here report an update of our imaging results using 123I-VIP (150-200 MBg/1 microgram/patient) in 169 patients. In patients with pancreatic adenocarcinomas without liver metastases, the primary/recurrent tumor was visualized in 16 of 18 patients (89%) and liver metastases were imaged in 15 of 16 patients. In 11 of 12 patients with colorectal adenocarcinomas, the primary/recurrent tumor (92%) was imaged by 123I-VIP. Also, in 21 of 25 patients, liver metastases (84%); in 3 of 6 patients, lung metastases (50%); and in 4 of 5 patients, lymph-node metastases (80%) were imaged by 123I-VIP. In 10 of 10 patients with gastric adenocarcinomas, the primary/recurrent tumor; in 3 of 4 patients, liver metastases; and in 2 of 2 patients, lymph-node metastases were visualized by 123I-VIP. 123I-VIP localized primary intestinal carcinoid tumors in 15 of 17 patients (88%) and 8 of 10 primary insulinomas (80%). We conclude that the 123I-VIPR scintigraphy localizes intestinal adenocarcinomas and endocrine tumors as well as metastatic tumor sites.