The authors report the case of a 26-year-old woman, with a palpable abdominal mass, dyspepsia, pain and weight loss. These symptoms were caused by a non-functioning or biologically inactive neuroendocrine tumour (BINT), weighing 510 g and located in the tail of the pancreas. The treatment opted for was a surgical resection consisting in a distal pancreatectomy. The results of the operation were satisfactory and the woman is now alive and in good health, without recurrence, after 7 years. The authors then go on to analyse the concept of non-functioning neuroendocrine tumours and the problems relating to their symptoms, location and nature. These tumours, which arise, from the pancreatic islet cells, fail to produce a clinical syndrome owing to insufficient peptide production or insufficient release, or concurrent secretion, of inhibitory peptides by the tumour or production of biologically inactive molecular forms of the peptides (without clinical effects). The value of tumour markers and the indications and type of surgery are also discussed according to the different patterns of tumour spread (local, locoregional and metastatic disease). It is stressed that a complete surgical resection is the only curative treatment for these tumours. Encouraging results have been recently obtained by adjuvant treatment with somatostatin analogues, chemotherapeutic agents and/or inteferon.