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We examined the accuracy of noninvasive predictions of pulmonary artery pressure (P), flow (Q), and resistance (R) by means of main pulmonary artery blood velocities and diameters measured with Doppler echocardiography (DE). The ratio of noninvasive acceleration time to ejection time (AN) was correlated to invasively determined mean pulmonary artery pressure (PI) and resistance (RI). Noninvasive flows were correlated to thermodllution flows (QI). Simultaneous invasive and noninvasive measurements were made in nine adult patients (ages = 22 to 73 years). The results were: PI= 87 − 152AN, r= 0.90, SEE = 7 mm Hg, p< 0.05; RI= 899 − 1722AN, r= 0.79, SEE = 121 dynes · sec · cm−5, p< 0.05; and QI= −0.3 + 1.21QN, r= 0.95, SEE = 0.81 L · min−1, p< 0.05. We then used these equations prospectively to predict PI, RI, and QIin 21 of 25 (83% technically adequate) consecutive patients. PI, RI, and QIranged from 10 to 35 mm Hg, 39 to 456 dynes · sec · cm−5, and 3.51 to 8.39 L · min−1, respectively. Results were: PI= 0.80P + 3, r= 0.72, SEE = 6 mm Hg, p< 0.05; RI= 0.75R − 12, r= 0.64, SEE = 77 dynes · sec · cm−5, p< 0.005; and QI= 0.87Q + 0.38, r= 0.83, SEE = 0.86 L · min−1, p< 0.05. These results suggest that DE predictions of pulmonary artery pressure, flow, and resistance correlate significantly with values subsequently obtained at catheterization.