Background: Carcinoid syndrome occurs in about 10 % of patients with carcinoid tumors. Objectives: The main objective of the present study was to determine the presence of the carcinoid syndrome in the group of patients with the carcinoid tumor. Subjects and methods: 43 pts. (22 w/21 m) with carcinoid tumors (M group - 26 pts. with metastatic disease, B group - 17 pts. after resection of the primary tumor without known metastases at the time of the investigation) were included in the study. We estimated the presence of the carcinoid syndrome in all patients. The urinary excretion of 5-HIAA was performed and echocardiography were done. Results: The amount of the 5-hydroxyindolacetate acid in urine in pts. with metastatic carcinoid was statistically significant higher than in the pts. without metastases (p < 0,001). The carcinoid syndrome in metastatic group we found in 10 patients. Flush had 9, diarhoe 7 pts., and cardiac involvement with endocardial fibrosis had 3 pts. During the treatment with lanreotide the amount of 5-HIAA in urine decreased from 1155 (207,6 - 1406) to 471 (96,6 - 1000)
mol/24 h (p < 0,05). During the follow up period 3 patients with carcinoid syndrome died.

        Key words: Carcinoid - Flush - Endocardial fibrosis - 5-hydroxyindolacetic acid (5-HIAA)