The aim of this study was to assess the value of echocardiographic contrast in measuring systolic pulmonary artery pressures. Thirty-four patients with an average age of 61 +/- 15 years undergoing right heart catheterisation had a simultaneous measurement of systolic pulmonary artery pressures by catheter and colour-coded Doppler echocardiography under basal conditions and after injection of 5% dextrose agitated with 1 cm3 of air to form microcavitations. The Doppler echocardiographic measurements were performed after withdrawal of the catheter into the inferior vena cava before and after injection of contrast. Patients were divided into two groups according to the pulmonary artery pressures at catheterisation: Group I, comprising 11 patients with systolic pulmonary artery pressures of less than 35 mmHg; Group II, comprising 23 patients with systolic pulmonary artery pressures of over 35 mmHg; The injection of contrast significantly increased the number of patients in whom systolic pulmonary artery pressures could be calculated from the Doppler signal of tricuspid regurgitation (TR) in Group I (control: 18%; contrast: 100%, p < 0.01) and Group II (control: 65%; contrast: 96%, p < 0.05). There was a close correlation between the catheter and Doppler measurements of the trans-tricuspid valve pressure gradients before and after injection of contrast in Group I (n = 11, r = 0.85, p = 0.001, with an estimated standard error (ESE) = 3.8 mmHg) and in Group II (control: n = 15, r = 0.89, p = 0.001, ESE = 10.5 mmHg, and after contrast: n = 22, .r = 0.90, p = 0.001, ESE = 7.95 mmHg) with the catheter in the right ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)