We evaluated the relationship between admission renal function (as assessed by estimated glomerular filtration rate (eGFR)), hyperglycemia, and acute insulin resistance, indicated by the homeostatic model assessment (HOMA) index, and their impact on long-term prognosis in 825 consecutive patients with ST-elevation myocardial infarction (STEMI) without previously known diabetes who underwent primary percutaneous coronary intervention (PCI). Admission eGFR showed a significant indirect correlation with admission glycemia (Spearman's ρ -0.23, P < 0.001) and insulin values (Spearman's ρ -0.11, P = 0.002). The incidence of patients with admission glycemia ≥140 mg/dl was significantly higher in patients with eGFR <60 ml/min/m(2) (P < 0.001) as well as the incidence of HOMA positivity (P = 0.002). According to our data, a relationship between renal function and glucose values and acute insulin resistance in the early phase of STEMI was detectable, since a significant, indirect correlation between eGFR, insulin values, and glycemia was observed. Patients with renal dysfunction (eGFR <60 ml/min/1.73 m(2)) exhibited higher glucose values and a higher incidence of acute insulin resistance (as assessed by HOMA index) than those with normal renal function (eGFR ≥60 ml/min/1.73 m(2)). The prognostic role of glucose values for 1-year mortality was confined to patients with eGFR ≥60 ml/min/m(2), who represent the large part of our population and are thought to be at lower risk. In these patients, an independent relationship between 1-year mortality and glucose values was detectable not only for admission glycemia but also for glucose values measured at discharge.