AIM: The aim of this study was to assess the value of plasma chromogranin A (CgA), a protein produced by neuroendocrine cells, in the diagnosis of neuroendocrine tumours. METHODS: Eighty subjects with neuroendocrine tumours were studied. Thirty-four had carcinoids, 21 nonfunctioning endocrine pancreatic tumours, 17 multiple endocrine neoplasia type 1 (MEN 1) (six of these also had gastrinomas), and eight had functioning pancreatic tumours (four gastrinomas, two glucagonomas, two somatostatinomas). Twenty-eight healthy subjects were studied as controls. A fasting plasma sample was obtained from each subject, and CgA plasma levels were measured by the ELISA method using a kit (Dako A/S, Denmark). RESULTS: In control subjects, plasma CgA values were below 5 U/l. Among the patients, 20 of the 34 with carcinoid tumours, 12 of the 21 with nonfunctioning pancreatic tumours, nine of the 17 with MEN 1 (including the six with gastrinomas), and the four gastrinomas of the eight functioning pancreatic tumours, i.e. overall, 45 of the 80 patients (56.3%) had abnormally high CgA values (22-961 U/l). Most of the patients with elevated CgA values, except nine of the 10 with gastrinomas, had multiple liver metastasis. CONCLUSIONS: The results show that the diagnostic value of plasma CgA in neuroendocrine tumours is relatively low; it may be of some interest only in patients with advanced disease and liver metastasis. Gastrinoma seems to be an exception, because in this tumour high CgA values are generally found even in the absence of liver metastasis.