To study the aggregation activity of platelets in patients with ischemic heart disease depending on the long-term intake of acetylsalicylic acid (ASA). Material and methods. The study included: 116 patients with coronary artery disease with stable angina pectoris, taking a standard dose of aspirin 75 mg/day. during various terms. Patients with SSN were divided into 4 groups according to the duration of taking ASA. Platelet aggregation was measured using a laser platelet aggregation analyzer Alat-2 Biol, with computer processing according to the AGGR program. Adenosine diphosphate (ADP) in concentrations of 0.1, 1.0, 5.0 mmol/l was used as an inductor. The results of the study of patients taking ASA for more than 5 years showed that spontaneous aggregation and ADP-induced platelet aggregation were higher than in patients taking the drug for less than 5 years. Statistically significant differences were observed when compared with a group of patients taking ASA for less than a year (spontaneous aggregation of 1.7±0.09 (p<0.05), 0.1 μm ADP-induced aggregation of 6.58±0.86 (p<0.05), 1.0 μm ADP-induced aggregation of 16.51±1.63 (p<0.01), 5.0 μm ADP-induced aggregation 58.44±3.72 (p<0.01). Conclusion. Thus, the results showed that with an increase in the duration of aspirin intake, there was a change in both spontaneous and ADP-induced platelet aggregation with a statistically significant increase.