We investigated the effects of aspirin (300 mg/d), ticlopidine (500 mg/d) and their low-dose combination (aspirin 100 mg/d plus ticlopidine 250 mg/d) on the platelet aggregability using the Wu and Hoak method. Each treatment group consisted of 25 patients with acute ischemic stroke. Platelet aggregation ratios (PAR) were measured on the 1St (before treatment), 10th and 90th days in the treatment groups and compared with those of 25 control cases. On the first day, comparison of PAR in each treatment group with the control was significant, while the differences between treatment groups were not significant. On the 90th day, differences of PAR between aspirin and control were significant, but differences between the other treatment groups and the control group were not significant, indicating a lower anti-aggregant efficacy of aspirin.