Most gastroenteropancreatic tumours express somatostatin receptors, allowing imaging using radiolabelled somatostatin analogues. Octreotide can be modified by coupling a DTPA moiety to the N-terminal D-phenylalanine to allow labelling with In111. We studied the comparative effectiveness of this radiopharmaceutical in identifying tumour extent. Twenty-two patients with metastatic gastroenteropancreatic tumours were scanned using [111In-DTPA-D-Phe1]-octreotide. In 11 patients with the carcinoid syndrome, one of six primary lesions was identified by CT scanning and by [111In-DTPA-D-Phe1]-octreotide scanning. Hepatic metastases were present in all patients, 9 of whom had positive scintigraphy. Two other sites of intra-abdominal uptake and four distant sites, not previously identified, were demonstrated. Five other distant sites were confirmed to be carcinoid metastases. All 11 patients with other gastroenteropancreatic tumours had positive scans, demonstrating 7/9 primary lesions, 12 intra-abdominal lesions, including hepatic metastases in all cases, and one distant lesion, all previously identified. Thus [111In-DTPA-D-Phe1]-octreotide imaging effectively identified the extent of metastatic disease from gastroenteropancreatic tumours, and confirmed lesions whose significance was uncertain following previous imaging procedures.