Continuous-wave Doppler echocardiography was used to estimate peak pulmonary artery (PA) pressure in 104 infants and children, aged 4 days to 16 years, with normal hearts (control group) and 43, aged 29 days to 13 years, with various kinds of heart disease (patient group). The Doppler transducer was directed toward the right ventricular outflow tract and angled until the maximal velocity signal was reached. Doppler velocity time intervals were measured as follows: acceleration time (AT), from the onset to the peak of the velocity curve; and ejection time (ET), from the onset to the termination of the velocity curve. In the control group, AT corrected through dividing by the RR interval of the electrocardiogram (ATc), and AT/ET by dividing by the square root of the RR interval (AT/ETc), were independent of body surface area. In the patient group, peak PA pressure had a significant inverse correlation with both ATc (r = -0.78) and AT/ETc (r = -0.87). Thus, AT/ETc derived from continuous-wave Doppler echocardiography is a good quantitative predictor of peak PA pressure in infants and children.