This retrospective analysis compared clinical outcomes of patients who underwent stenting with > or =3 sirolimus-eluting stents (SESs) with those who received a single SES. SES (Cypher) implantation for single vessels is proved to be effective and durable, but knowledge regarding the safety and effectiveness of multiple stenting with SESs is currently limited. In total, 929 consecutive patients who received SESs were identified; 63 received > or =3 SESs (multi group) and 866 received 1 SES (single group). The multi group had more non-Q-wave myocardial infarctions (MIs) during the index hospitalization (p = 0.02). At 30-day follow-up, death, Q-wave MI, subacute thrombosis, and major adverse cardiac events were higher in the multi group than in the single group. At 6 months, death, Q-wave MI, target lesion revascularization, and major adverse cardiac events continued to be higher in the multi group. Using multivariate analysis, > or =3 SES implantations, American College of Cardiology/American Heart Association type C lesions, and cardiogenic shock were identified as independent predictors for 6-month major adverse cardiac events. In addition, patients in the multi group had a significantly lower survival rate than patients in the single group (p <0.0001). Patients who required > or =3 SES implantations developed increased periprocedural non-Q-wave MI and worse adverse clinical outcomes at 30 days and 6 months compared with patients who required a single SES implantation. In conclusion, when patients present with multiple coronary lesions, percutaneous coronary intervention with multiple SESs should be undertaken with great caution.