14 patients with metastatic endocrine gastro-entero-pancreatic carcinoma (6 patients with Carcinoid-syndrome, 3 with gastrinoma and 5 with non-functioning tumor) have been treated with Octreotide 3 x 200 micrograms/die plus Interferon-Alpha 3 x 5 Mio U/week after documented tumor progression during preceding Octreotide-monotherapy. 6 out of 14 patients responded favourable to the treatment: one patient with partial regression and 5 patients with stillstand of tumor growth. In only one patient initial tumor stillstand for 6 months was followed by tumor progression whereas in five patients a beneficial effect on tumor growth could be documented up to 34 months. Inhibition of tumor growth and tumor progression was not necessarily paralleled by respective changes in peripheral hormone levels. These results should initiate a controlled prospective study to prove the hypothesis that in patients with metastasized endocrine gastro-entero-pancreatic tumors the combination of Octreotide and Interferon-Alpha is superior to monotherapy with Octreotide or Interferon-Alpha and to identify those patients who respond to this combined therapy.