A 47-year-old man presented with episodes of altered mental state initially felt to be complex partial seizures, but which were in fact hypoglycaemic episodes. An insulinoma was confirmed and eventually localised. He underwent an abdominal computed tomography scan and intraoperative laparoscopy, but required selective venous sampling to localise the tumour. Fifteen months after his surgery there is no evidence of recurrence of his insulinoma.