Diabetes mellitus is associated with endothelial dysfunction and platelet activation that may contribute to the occurrence of no-reflow. We postulate that optimal glycemic control is associated with the lower risk of no-reflow and better outcomes. Diabetic patients who underwent primary angioplasty for myocardial infarction from January 2001 to June 2004 were analyzed. No-reflow was defined as TIMI flow < 3 in the absence of mechanical obstruction. Patients were divided into 2 glycemic control groups according to the HbA1c value: optimal (less than or equal to 7%), and suboptimal (> 7%). A total of 183 diabetic patients (93% noninsulin-requiring) were included for analysis. The median HbA1c of the optimal (n = 37) and suboptimal (n = 146) glycemic control groups were 6.5% and 8.5%, respectively. Compared to the suboptimal glycemic control group, the optimal glycemic control group was older, likely to have hypertension, previously suffered a stroke, have renal failure and a higher baseline creatinine. No-reflow occurred in 16% of the optimal and 18% of the suboptimal glycemic control groups. Multivariate analysis showed that optimal glycemic control was not associated with a lesser occurrence of no-reflow (OR 1.27, 95% CI 0.19-8.29; p = 0.807). The optimal glycemic control group had 30-day survival (90% versus 93%; p = 0.698) and 30-day event-free survival (84% versus 86%; p = 0.695) rates similar to the suboptimal glycemic control group. Among diabetic patients undergoing primary angioplasty, optimal glycemic control was not associated with a lesser occurrence of no-reflow or better 30-day outcomes.