Myocardial ischemia and reperfusion result in ventricular and endothelial dysfunction. We investigated the hypothesis that nitrates, prevent ischemia-reperfusion injury and enhanced myocardial recovery. Twenty isolated guinea-pig hearts were perfused with Krebs-Henseleit Buffer (KHB) by using Langendorff apparatus. We allocated the animals into two groups. In the study group (Group I), nitroglycerin (NTG) was added into KHB and in the control group (Group II) perfusion was performed without NTG. Myocardial functions (heart rate, developed pressure and dP/dt(max)); Nitric oxide (NO), malondialdehyde (MDA) and glutathione (GSH) levels of the perfusate and heart tissue, were obtained as data. Percentage change of heart rate was 95.8 +/- 8.4 in the NTG group and 87.3 +/- 8.2 in the control group; Percentage change of developed pressure was 68.1 +/- 10.4 and 55.9 +/- 8.6 in the study group and in the control group respectively (p = 0.003); Percentage change of dP/dt was 67.2 +/- 10.3 in the study group and 54.4 +/- 5.3 in the control group (p = 0.009) at the postreperfusion period. Tissue NO level was 0.79 +/- 0.13 mu mol in Group I and 0.54 +/- 0.12 mu mol in Group II (p = 0.0003). Tissue MDA level was 30.3 +/- 5.4 nmol/gr-tissue in the study group and 53.5 +/- 4.2 nmol/gr-tissue in the control group (p = 0.002). Tissue GSH levels were 0.98 +/- 0.09 and 0.80 +/- 0.07 mu mol/gr-tissue in Group I and Group II, respectively (p = 0.0009). The perfusate MDA levels decreased and GSH levels increased in the study group (p = 0.005 and p = 0.01, respectively). Ischemia-reperfusion injury of the heart can be reduced by using NTG in the preischemic period.