A 3-year study assessed the prevalence and causes of severe treatment-related hypoglycaemia in type 2 diabetes mellitus patients admitted to hospital in Piraeus. Out of the 2858 patients admitted, 207 (7.2%) had severe hypoglycaemia: 72 were being managed with insulin, 132 oral hypoglycaemic drugs and 3 combined insulin/oral drugs. Only 28.5% of patients were attending a diabetes clinic. The cause of the hypoglycaemic attack could be determined for 86.1% of cases; 30.8% were due to a missed meal. Interviews showed that education and level of knowledge about diabetes mellitus, and particularly hypoglycaemia symptoms, was inadequate. Logistic regression analysis showed that knowledge about diabetes mellitus correlated with educational status and with follow-up in a diabetes clinic.