Many studies have suggested an imbalance between proinflammatory and anti-inflammatory markers in acute myocardial infarction (AMI). Interleukin 4 (IL-4) shows mainly anti-inflammatory activities. Interferon-gamma (IFN-γ) is a proinflammatory cytokine secreted by Th1 lymphocytes. Severe systolic left ventricular (LV) dysfunction following AMI is one of the major risk factors for poor prognosis. The aim of this study was to evaluate whether IL-4 and IFN-γ concentrations can serve as the correlates of impaired left ventricular function. Fifty-three patients with AMI were enrolled and divided into two groups depending on their ejection fraction (EF): group 1 with EF ≤ 30% (N = 10) and group 2 with EF >30% (N = 43). All patients underwent coronary angiography followed by percutaneous coronary intervention (PCI). Blood samples were taken (1) before, (2) immediately after, (3) 2 h after, and (4) 72 h after PCI. A receiver-operating characteristic (ROC) analysis was planned to identify possible cutoff values to predict LV dysfunction. There was no sex difference between the two groups. The rate of hypertension and diabetes mellitus was also similar. Median concentrations for IL-4 (pg/ml) were: (1) 13.4 versus 17.2 (p = 0.0001), (2) 16.8 versus 18.6 (p = 0.01), (3) 17.2 versus 17.6 (p = NS), and (4) 17.6 versus 17.2 (p = NS). Median concentrations for IFNγ (pg/ml) were: (1) 0.3 versus 1.9 (p = 0.00001), (2) 2.1 versus 1.6 (p = NS), (3) 0.4 versus 0.9 (p = NS), and (4) 0.9 versus 1.1 (p = NS). The area under the ROC curve (AUC) analysis is presented in the table below. Reported results suggest the high diagnostic value of IL-4 measurements before and immediately after PCI as the correlates of impaired LV dysfunction, whereas only IFN-γ measurement before PCI had a high diagnostic value. Measurements performed later on have no predictive value. Cutoff value AUC Sensitivity (%) Specificity (%) PPV (%) NPV (%) p IL-4 (a) ≤ 15.0 0.89 100 79 52 100 0.0001, IL-4 (b) ≤ 17.2 0.75 100 67 42 100 0.0007, IFNγ (a) ≤ 0.3 0.94 100 91 71 100 0.0001.