Pentoxifylline, a xanthine derivative with vasoactive and hemorheologic properties, was studied in regard to effect on central hemodynamics in ten patients with congestive heart failure due to aortic or mitral valve disease, mainly in NYHA group III or IV. The drug was infused intravenously in a dose of 4 mg/kg b.w. during a stable hemodynamic situation after valve replacement. The heart rate, systemic blood pressure, central venous and pulmonary artery pressures and cardiac output were recorded, and the stroke volume, cardiac index and systemic vascular resistance were calculated. Significant increase in cardiac output from the baseline value of 4.92 l/min was found 5-10 min (+22.6%) and 25-30 min (+19.5%) after pentoxifylline infusion. Cardiac index similarly increased from baseline, 2.73 dsc-5 (+22.3 and +18.3, respectively). The systemic vascular resistance showed significant decrease at the same intervals (-20.6 and -15.5%). The heart rate and stroke volume were significantly increased after 5-10 min. The systemic mean blood pressure and the pulmonary artery and central venous pressures showed no significant changes. There were no adverse effects of pentoxifylline.