There is little information about the incidence of the side-effects of clopidogrel in Japanese patients undergoing coronary stent implantation. The present study included 334 consecutive patients who were given clopidogrel (75 mg daily) after coronary stent implantation. Aspirin (100 mg daily) was used indefinitely. Clopidogrel was prescribed for at least 4 weeks in patients with bare metal stents and indefinitely in those with drug-eluting stents (DES). The duration of clinical follow-up was 164.7 ± 139.0 days. Half of the patients underwent stenting because of acute myocardial infarction. DES were used in 38% of the patients. Definite early stent thrombosis occurred in one patient (0.31%). There was one definite late stent thrombosis (0.31%). Side-effects of the clopidogrel were observed in 16 patients (4.9%). Liver dysfunction occurred in seven patients (2.1%), skin rash in six (1.8%), and bleeding in three (0.9%). There was no neutropenia or thrombocytopenia. The results of this study show that prescribing clopidogrel as well as aspirin is a safe treatment for Japanese patients undergoing coronary stenting.