We examined if a loss-of-function polymorphism in the P2X(7) receptor (1513C) corresponded with circulating interleukin(IL)-18 concentrations in heart failure (HF) patients. IL-18 values were significantly elevated in HF subjects compared to healthy control subjects. No association was seen between the polymorphism and IL-18 concentrations in HF patients. In HF patients, IL-18 values had an inverse relationship with ejection fraction, mean arterial pressure and body mass index, while high IL-18 concentrations were associated with increased mortality.