In a European multicenter trial, a combination of conventional imaging methods (CIM) detected tumor sites in 88% of patients with gastroenteropancreatic endocrine tumors, whereas [111In-DTPA-D-Phe1]-octreotide scintigraphy was positive in 80% of the patients. The highest success rates of [111In-DTPA-D-Phe1]-octreotide scintigraphy were observed in patients with glucagonomas (100%), vipomas (88%), carcinoids (87%) and nonfunctioning islet cell tumors (82%). In addition to 297 out of 388 localizations found with CIM [111In-DTPA-D-Phe1]-octreotide scintigraphy revealed another 166 unsuspected lesions of which 40% were subsequently confirmed as true-positive findings based on the results of additional imaging procedures or histology obtained during a follow-up period. Overall, the scintigraphic findings led to management changes in 40% of the 235 patients for whom these data were available.