The relationship between chest X-ray findings and NYHA classification or haemodynamic parameters (ejection fraction, end-diastolic and end-systolic volumes by echocardiography, right atrial pressure--RAP, pulmonary artery pressure--PAP and pulmonary wedge pressure--PAWP by right heart catheterization) was evaluated in 44 and 22 patients with chronic congestive heart failure, respectively. In chest X-ray, the cardiothoracic index (CTI) and authors' own classification of pulmonary congestion (PCG) of classes 0, 1 and 2 were used. A significant correlation was found between CTI and NYHA classification or haemodynamic parameters, and between PCG (classes 0 and 2) and echocardiographic parameters or right heart pressures (EDV, ESV, RAP, PAP, PAWP), but there was no significant relationship between X-ray and left ventricular ejection fraction. For a PAWP higher than 18 mmHg and PCG class 2, the sensitivity of X-ray was 86% and specificity 80%. The authors conclude that chest X-ray provides reliable information about the haemodynamic parametres, comparable to echocardiographic and catheterization data.