According to official statistics, malignant insulinomas account for a small fraction of gastroenteropathic endocrine neoplasms, the majority of insulinomas being essentially benign tumours. This paper reports a clinical case of malignant insulin-producing neuroendocrine tumour of the pancreas tail in a 28 year-old woman. She had multiple liver metastases and organic hyperinsulinism. Results of comprehensive examination of the patient at the Endocrinological Research Centre including laboratory diagnostic data and their evaluation are presented. Her surgical treatment was accomplished in N.N. Burdenko Facultative Surgery Clinic, I.M. Sechenov Moscow Medical Academy. Treatment strategy in the post-operative period and follow-up observations are described.