Background: Fasting blood glucose levels (FG) are related to adverse outcomes in all patients with acute myocardial infarction (AMI), probably more so than admission glucose (AG) levels. We sought to examine this correlation among patients with ST-elevation AMI treated with primary percutaneous coronary interventions (PPCI). Methods: Our cohort included 570 consecutive patients without previously known diabetes mellitus who were treated with PPCI for ST-elevation AMI. The cohort was divided according to FG levels measured on days 2 to 4 of hospitalization, while the patients were clinically stable: FG ≤100 mg/dL, normal range; FG 100-110 mg/dL, mildly impaired FG; FG 110-126 mg/ dL, significantly impaired FG; FG ≥126 mg/dL, diabetic range. Results: One third of the cohort had impaired FG, of whom 20% had FG levels in the diabetic range. There was a weak correlation between AG and FG levels (r = 0.38, P = .000). In the multivariate analysis, adjusted for AG quartiles, patients with FG ≥110 mg/dL were more likely to die within 30 days (odds ratio 1.7, 95% CI 1.03-2.70, P = .04). Admission glucose levels did not independently impact on 30-day mortality (odds ratio 0.99, 95% CI 0.50-1.90, P = .96). Conclusions: Fasting blood glucose levels may be routinely assessed among patients with ST-elevation AMI undergoing PPCI, possibly aiding in risk prognostication and the tailoring of therapy.