This study sought to examine the effects of insulin-induced hypoglycaemia on anger state, and to describe the associations between change in the anger state and measures of anger trait and anger expression (assessed using the State-Trait Anger Expression Inventory). A hyperinsulinaemic glucose clamp was used to achieve controlled euglycaemia (5.0 mmol/L) and hypoglycaemia (2.6 mmol/L) in 18 nondiabetic subjects and 30 people with insulin-dependent diabetes mellitus (IDDM). Subjects underwent both hypoglycaemic and euglycaemic conditions, separated by 2 weeks, in a counterbalanced order. During each study condition subjects were asked to complete a questionnaire on anger state. Results at euglycaemia and hypoglycaemia were compared, and differences between the conditions were correlated with measures of anger trait and anger expression. Hypoglycaemia caused both nondiabetic and IDDM subjects to report a significant increase in feelings of anger, despite being in a nonconfrontational setting. However, there were no clear associations between an individual's change in reported anger and measures of anger trait and anger expression. No association was found between the change in anger state and the intensity of an individual's symptomatic response to hypoglycaemia.