To investigate if interlukin-18 cytokine (IL-18) and thromboxane A2 (TXA2) participate in the development and the progression of congestive heart failure (CHF) in children. Plasma levels of IL-18 and TXA2in 40 children with various degrees of CHF were correlated to severity, functional class, response to treatment and their echocardiographic parameters. Forty age and sex matched clinically free infants were included as a control group. The children suffering from CHF were found to have statistically higher plasma levels of IL-18, and correlated positively with the severity of the clinical class of heart failure. The studied children had statistically significant higher plasma levels of thromboxane B2 than the controls. Our study findings suggests that cytokines, namely IL-18 and the eicosanoind TxA2, much like the neurohormones, may represent other classes of biologically active molecules that are responsible for the development and progression of heart failure.