Heart Failure (HF) is characterized by activation inflammatory mediators that contributes to the disease progression. Brain natriuretic peptide (BNP) plasma levels increase in HF with a prognostic significance. The aim of this study was to evaluate the expression and activity of inducible nitric oxide synthase (iNOS) in peripheral blood mononuclear cell (PBMC) extracted from patients and a possible linear correlation between iNOS and plasma levels of BNP in decompensated chronic HF (DCHF) patients. To establish the DCHF, thirty-five male patients were evaluated. All patients were venesected within 24 h of admission to exclude an inflammatory state through evaluation of c-reactive protein. Only twenty subjects showed symptoms of DCHF were included in the study. Other patients were included in the control group. In DCHF, left ventricular ejection fraction (LVEF) percent was reduced and systolic pulmonary artery pressure (PAPs) was increased. Furthermore, iNOS expression and BNP plasma levels were significantly higher in patients with DCHF as compared to controls group. These findings indicate that in DCHF patients, iNOS activity exhibits a significant linear correlation with plasmatic BNP level.