s To compare the clinical effects of intravenously and orally administered aspirin in the treatment for acute coronary syndrome (ACS),and to evaluate the adverse effects of intravenous administration of aspirin.Methods One hundred and twenty-five patients with unstable angina pectoris or acute myocardial infarction were randomized into three groups:group 1 received intravenous aspirin (300mg/d,n =40),while groups 2 (n =42) and 3 (n =43) received orally administered aspirin (100mg/d and 300mg/ d,respectively).The control group included 30 patients with no heart disease or blood disease,and they had never taken aspirin and clopidogrel.Blood samples were taken at 2nd and 7th day of hospitalization.Platelet aggregation and the level ofplatelet activation marker CD62p were measured and compared among the groups.Patients were followed up for 6 months for the occurrence of major adverse cardiovascular events.Results There were no statistically significant differences in the decrease in adenosine diphosphate (ADP)-induced platelet aggregation rate (12.01±10.45%,6.76±14.62% and 9.73±16.72% for group 1,group2 and group 3,respectively),the decrease in arachidonic acid (AA)-induced platelet aggregation rate (6.73±11.34%,6.95±12.45% and 7.57±13.11%,respectively),and the decrease in CD62p level (10.89±18.62%,8.92±11.57% and 7.05±15.67%,respectively).At six months,there were 4 deaths (10%) in group 1,4 deaths (9.5%) in group 2 and 5 deaths (11.6%) in group 3 (P＞0.05).Conclusions Intravenous administration of aspirin provides a new approach as an anti-platelet treatment for ACS patients,especially those who can not tolerate oral administration of aspirin.(J Geriatr Cardiol 2008;5:212-216)