In 160 patients admitted during the first 8 days following myocardial infarction during the period November 1st 1974 - March 15th 1975, the prevalence of diabetes was 17%. Among 655 patients treated for a month in a convalescence centre following the acute phase of myocardial infarction during the period January 1st 1974 - March 15th 1975, the prevalence of diabetes was 17.5%. Mortality rate during the first 8 post infarction days was 28% in diabetics and 13% in non-diabetic patients in the coronary care Unit; over the subsequent month, the mortality rate was 7.7% in diabetics and 3.7% in non-diabetics while at the convalescence Centre. The higher mortality rate from myocardial infarction in diabetics could not be contributed to a greater severity or more wide spread nature of the coronary artery disease as evidenced by the results of coronary cineangiography performed in diabetic and non-diabetic patients with severe ischaemic heart disease. In the cases in which an aorto-coronary by-pass was performed, there was no apparent difference in the response of diabetics compared to non-diabetic subjects. Despite progress in intensive treatment of myocardial infarction, mortality rate of this disease in diabetics remain very high. Reduction of the incidence of ischaemic heart disease in diabetics requires early identification and reversal of all of the many risk factors for arterial disease.