The insulin autoimmune syndrome (IAS) is the third leading cause of spontaneous hypoglycaemia in Japan. Here, we describe the second Dutch case. An 81-year-old man was analysed for collapse and attacks of disorientation, and was found to be hypoglycaemic during such an episode. The performed fasting test appeared to be positive. High levels of insulin and C-peptide postprandially and insulin antibodies were found. IAS was diagnosed.