Neuroendocrine tumors of the gastroenteropancreatic system present not only a diagnostic but also a therapeutic challenge. In case of limited neuroendocrine tumor disease curative surgery is the goal to aim for. But in patients with metastatic disease (palliative) surgery may be indicated, too. (Chemo-) Embolization should to be considered for liver metastases causing severe local symptoms. Recently, biotherapy with somatostatins or interferon-α has revolutionized the treatment of metastatic neuroendocrine tumor disease of the gastroenteropancreatic system. Both somatostatins and interferon-α are mostly effective in controlling the carcinoid syndrome; they lead to significant tumor reductions at least in some cases and thereby improve the quality of life and possibly lengthen survival. For patients with anaplastic neuroendocrine tumors or with advanced neuroendocrine tumor disease of the pancreas, chemotherapy may still be the first-line treatment modality; the response rate is 40-70%. Present clinical trials investigate the efficacies of combinations of different biotherapie