Background-Diabetes mellitus adversely affects outcomes in patients undergoing percutaneous coronary intervention.The association of baseline hemoglobin A1c (HbA1c) at the time of percutaneous coronary intervention with long-term mortality is unknown. Methods and Results-Consecutive patients with diabetes mellitus undergoing percutaneous coronary intervention between 1998 and 2008 were identified from our institutional database. Characteristics and outcomes of patients were compared based on HbA1c categories (≤7%, 7.1%-8.0%, 8.1%-9.0%, 9.1%-10.0%, and >10.0%