One hundred and fifty-eight patients with insulin dependent diabetes mellitus attending two Auckland outpatient clinics answered a questionnaire about hypoglycaemia. Almost all (98%) had experienced hypoglycaemic episodes and for 30% these were a major problem. Seventy-seven percent reported nocturnal hypoglycaemia, 39% of whom required external assistance during episodes. Forty-three percent had experienced coma, or convulsions during hypoglycaemia and a small group, 7%, had recurrent severe episodes. Twenty percent carried no diabetic identification and 13% did not routinely carry a glucose supply. Only 38% of patients kept glucagon at home. Forty percent of patients driving vehicles had experienced hypoglycaemia while driving and 13% reported traffic accidents attributed to hypoglycaemia. Hypoglycaemia is a major problem for many patients taking insulin. Improved education, wider availability of glucagon and more liberal glycaemic control of patients with problematic hypoglycaemia may be advisable.