Surgery has always been considered to be the primary treatment in patients with neuroendocrine gut and pancreatic tumors, but a significant number of patients present liver metastases already at the first visit. There is obviously a need for effective medical treatment and in the present paper we report our experience of treatment with chemotherapy, the somatostatin analogue SMS 201-995 and interferons. In 30 patients with malignant endocrine pancreatic tumors, chemotherapy including streptozotocin plus 5-fluorouracil had an objective response rate of 63% with a mean duration of the objective response of 17.4 months. There was a difference between clinically functioning and nonfunctioning tumors, which had objective response rates of 68% and 50% and mean response duration of 21 and 9.4 months respectively. The new somatostatin analogue SMS 201-995 was used in 10 patients giving an objective response rate of 40% with a mean duration of 13.5 months. In a series of 22 patients treated with human leukocyte interferon, an objective response rate of 77% was obtained with a mean duration of 8.5 months. A combination of streptozotocin plus 5-fluorouracil gave an objective response rate of 10% with a mean duration of 2.7 months among 31 patients with midgut carcinoid tumors. The somatostatin analogue SMS 201-995, tested in 22 patients with carcinoid tumors, gave an objective response rate of 28% with a mean duration of 18.5 months. Interferon has been tried in three separate studies. The first study, including 36 patients with malignant carcinoid tumors treated with human leukocyte interferon, showed an objective response rate of 47% with a mean duration of 34 months. In a randomized controlled study, where human leukocyte interferon was compared with streptozotocin plus 5-fluorouracil including 10 patients in each arm, no objective response was obtained during the six months' observation in the group of patients receiving chemotherapy, whereas 50% responded in the interferon-treated group. In the third study, IFN-alpha 2b or IntronA was tested in 20 patients with malignant carcinoid tumors and gave an objective response rate of 55% during a six-month observation period. With regard to these data chemotherapy and interferons seem to be equally potent in the treatment of malignant endocrine pancreatic tumors, whereas interferons seem to be superior to both chemotherapy and the somatostatin analogue SMS 201-995 in malignant carcinoid tumors. The somatostatin analogue has proved to be particularly useful in the treatment of patients with severe hormone-related clinical symptoms and in the perioperative period.(ABSTRACT TRUNCATED AT 400 WORDS)