The management of metastatic neuroendocrine tumors incorporates multimodal therapy with surgery, biotherapy, and chemotherapy. Tumor-targeted therapies using radiolabeled octreotide and metaiodobenzylguanidine (mIBG) represent a novel treatment approach. The aim of this study was to evaluate the effectiveness of 131I-mIBG in the treatment of metastatic midgut carcinoid tumors. survival outcomes were assessed for patients treated at two regional cancer centers and then compared. One center used 131I-mIBG routinely in the management of metastatic carcinoid tumors (center A), and the other did not use this modality (center B). Only patients with histologically proven metastatic carcinoid tumor shown, or thought most likely, to be of midgut origin were included in the study. During the period 1980 to 2002, a series of 58 patients from center A with metastatic carcinoid tumor arising from the midgut underwent multimodality therapy with the addition of 131I-mIBG. Their median age was 64 years. The median dose of 131I-mIBG administered was 6751 MBq, and there was an average of 2.8 treatments per patient. During the same period, 58 patients with metastatic carcinoid were treated at center B with similar multimodality therapy without the use of 131I-mIBG therapy. Their median age was 65 years. Survivals at 3 and 5 years were 77% and 63%, respectively (95% CI 47-75), for group A. The 3- and 5-year survivals for group B were 56% and 47% (95% CI 34-59), respectively. The mean follow-up was 6.6 years for group A and 5.0 years for group B. Although retrospective in nature, this study suggests that the addition of 131I-mIBG therapy to the treatment protocol of patients with metastatic midgut carcinoid tumors prolongs survival.