The aim of this study was to discover the frequency and the symptoms of hypoglycaemic reaction and coma. One hundred type I diabetic patients answered an oral questionnaire and explained how they were awaken from their hypoglycaemicoma. The frequency of hypoglycaemic reaction was from one a day to one a year. 41 patients had nocturnal hypoglycaemic reactions. Our patients described 27 different symptoms of oncoming attack; however, not all of these symptoms was experienced by any one of the patients. Treatment of hypoglycaemic reaction was administered correctly but at the precise moment of the interview, 13% of patients had no carbohydrates with them. 42 patients had had hypoglycaemic reaction but no coma. Shared between 48 patients were 578 insulin years and 148 comas. Treatment of hypoglycaemic coma was variable: 20 patients remained at home receiving appropriate treatment; 33 were always hospitalised on attack and 20 were still comatous on each admission. The explanation of hypoglycaemic attack was variable; an emotional factor was given by 19% of patients. Both type I diabetic patients and their immediate entourage should be made aware of all the symptoms of oncoming attack and of the treatment of hypoglycaemic coma. Systematic glycemic auto control should testify to the existence of genuine hypoglycaemic reaction and perhaps diminish its supposed frequency.