Fifty-five patients with metastatic carcinoid tumor were treated with the long-acting somatostatin analogue octreotide. Nineteen received in addition alpha-interferon when octreotide had failed. During octreotide treatment reduced flush and/or diarrhea was seen in 70% of the patients, 37% showed > 50% decrease in urinary 5-HIAA for a median of 8 months. A further 49% experienced stabilization of their disease and only 14% progressed. One patient showed reduced tumor size. Of the 19 patients given alpha-interferon in combination with octreotide, 72% showed significant reduction in urinary 5-HIAA for a median of 10 months. Twenty-two percent became stabilized and only 6% progressed. A symptomatic improvement was seen in 49%. The combination was well tolerated. Our data confirm previous studies, showing that octreotide is useful for treatment of the carcinoid syndrome. Our results also indicate that the combination of octreotide and alpha-interferon might be of beneficial value for long-term management of this disease.