Hypoglycaemia induced by class 1A antiarrhythmic agents has been described. A case of cibenzoline-induced hypoglycaemia with favourable outcome is reported. The patient's age (84 years), increased renal impairment and malnutrition acted as facilitating factors. Blood insulin levels were normal in both absolute and relative values. Therapeutic overdosage in relation to age and renal function has been found in 20 out of 24 cases published or recorded by the French pharmacovigilance system. The mechanism of this hypoglycaemia is uncertain; absolute or relative hyperinsulinism has been detected in only 5 out of 14 controlled cases.