Noninvasive estimation of pulmonary arterial pressure is important for hemodynamic monitoring of patients with heart disease. In patients with tricuspid regurgitation (TR), the peak velocity of TR on continuous-wave (CW) Doppler can be used to estimate the systolic pulmonary arterial pressure (PAPs) using the simplified Bernoulli equation. We evaluated a new technique of contrast-enhanced CW Doppler for calculating PAPs in patients with trivial TR. Forty-one patients without visible TR detected by color Doppler, pulsed Doppler or CW Doppler were evaluated. Age ranged from 19 to 73 (55 ± 12) years old. Tricuspid flow signals were recorded on CW Doppler after intravenous administration of indocyanin green (ICG) or Albunex. PAPs was calculated as; PAPs = 4 × V²_TR + 10 mmHg, where V_TR is the peak velocity of TR. PAPs calculated using contrast-enhanced CW Doppler was compared with PAPs measured by the following cardiac catheterization. 1) TR signals were recorded using the contrast-enhanced CW Doppler technique in 39 of 41 patients (95%) after intravenous administration of contrast agents. 2) The error of estimate of PAPs using the contrast-enhanced CW Doppler technique was - 2.4 ± 7.5 mmHg, and the percent error was -10.7 ± 32.4% in all patients. In 20 of 39 patients (51%), the error of estimate was within ± 5 mmHg. 3) PAPs was overestimated by 12.2 ± 6.1 mmHg in patients with good contrast enhancement of TR signals. The contrast-enhanced CW Doppler technique is useful for estimating PAPs noninvasively in patients with trivial TR. It is better to assume the right atrial pressure as 3-5 mmHg, not 10 mmHg, in patients with good enhancement of trivial TR. Physiological TR may be enhanced by contrast agents in these patients.