In order to evaluate the value of impedance rheopneumogram (IRP) in predicting pulmonary arterial pressure (PAP) and pulmonary arterial hypertension (PAH) noninvasively and quantitatively, 150 patients with chronic obstructive pulmonary disease (COPD) were examined by IRP and right heart catheterization simultaneously. It was found that some parameters derived from IRP correlated well with PAP, the strongest correlation being demonstrated by Q-B/B-Y ratio (gamma = 0.74, p < 0.001) and Hs (gamma = -0.56, P < 0.001). We made a multi-stepwise regressional analysis and obtained an equation to predict PAP from IRP parameters: PAP (kPa) = [-2.26-5.05 x 1nHs + 27.02 x (Q-B/B-Y)] x 0.133 (gamma = 0.78, P < 0.001). Other 30 COPD patients were selected to assess the effectiveness of the equation. We found that the sensitivity and specificity of the equation in identifying PAH were 83% and 93% respectively.