Synonyms for gastroenteropancreatic endocrine tumours are 'endocrine tumours' and 'neuroendocrine tumours', and for pancreatic tumours 'islet cell tumours'. The term 'carcinoid' should only be used for endocrine tumours of the gastrointestinal tract and not for those of the pancreas. Endocrine tumours should be classified according to a recent World Health Organization proposal that provides clinically and prognostically important information. The prognosis of well-differentiated endocrine tumours is variable and, in general, favourable. However, we have few histological data from which to predict tumour growth and long-term prognosis in well-differentiated tumours. Poorly differentiated, small-cell tumours have an unfavourable prognosis. Patients with endocrine tumours have an increased risk of developing synchronous and metachronous non-endocrine malignancies. Most current treatment options are not supported by prospective, randomised and controlled trials.