A survey is given of the literature on the influence of prostaglandins on the lipid- and carbohydrate metabolism. Some common pathobiochemical features in the development of diabetes mellitus and the ischaemic heart disease are outlined, which became apparent by examinations of the fatty acid pattern in patients. Thus a biochemical basis for that epidemiologically well known fact is given, that diabetes represents a risk factor for the ischaemic heart disease. Some of the latest results from the experimental research suggest that the vascular complications occurring in chronic diabetes are caused by a decrease in the formation of prostacyclin and possibly by an increase in the thromboxane A2 production. Similar changes in the prostaglandin metabolism occur in the ischaemic heart disease and myocardial infarction, too, as experimental results have shown.