A study of 169 patients with coronary heart disease has shown that the duration and intensity of the inhibition of platelet aggregation following the single administration of 0.5, 1 and 1.5 g of aspirin is largely determined by the dose used. It has been established that in individuals sensitive to aspirin, the intake of 0.5 g of the drug causes a marked inhibition of platelet aggregation lasting for over 24 hours. A year-long follow-up of patients with myocardial infarction receiving 0.5 g of aspirin daily has demonstrated that platelet aggregation is consistently depressed throughout the entire period of observation.