ADP-induced platelet aggregation was studied in 28 patients with myocardial infarction randomized, at admission, into three groups. Conventional therapy with heparin and antianginal drugs was combined with aspirin (250 mg/day, n = 9), tiklid (500 mg/day, n = 9), tiklid (500 mg/day) + aspirin (250 mg/day, n = 10) in group 1, 2 and 3, respectively. Tiklid diminished platelet aggregation more effectively than aspirin on the disease day 7 and 21. Tiklid + aspirin combination suppresses platelet aggregation more than monotherapy with either of the drugs, provides insignificant attenuation of postinfarction angina but is associated with a high risk of hemorrhagic complications.