Although it has been shown that pulmonary flow velocity can be calculated from contrast M-mode echocardiographic tracings, the clinical value of this noninvasive method has not been established. We used contrast M-mode echocardiography to examine the flow velocity pattern at the pulmonary valve in 30 adults referred for diagnostic cardiac catheterization. In the 15 patients with normal pulmonary artery pressure (PAP) (mean pressure less than or equal to 20 mm Hg), midsystolic pulmonary flow velocity was significantly (p less than 0.001) higher (654 +/- 140 mm/sec) compared to the 15 patients with pulmonary hypertension (342 +/- 85 mm/sec, mean pressure greater than 20 mm Hg). Fourteen of the 15 patients with pulmonary hypertension exhibited an early systolic flow velocity peak, whereas all patients with normal PAP showed a dome-shaped systolic flow velocity profile with maximal flow velocity occurring in midsystole. A significant close correlation was found between the relative early to midsystolic flow velocity change and mean PAP (r = 0.96; p less than 0.001). Thus quantitative contrast M-mode echocardiography reliably differentiates patients with pulmonary hypertension from patients with normal mean PAP. In addition, this technique allows a noninvasive estimation of PAP.