Pulmonary arterial flow was examined in 60 normal children with a mean age of 8.5 +/- 3.7 years (range 3.3 to 17.9 years) and mean body surface area of 0.95 +/- 0.3 m2 (range 0.6 m2 to 1.7 m2) by pulsed Doppler echocardiography. Two distinct antegrade waveforms during diastole were detected. The peak velocities of early diastolic forward flow ranged from 20 to 30 cm/s (mean 26 +/- 4) and the late diastolic forward flow ranged from 16 to 29 cm/s (mean 23 +/- 3). The integrals of early diastolic forward flow ranged from 2.1 to 4.7 cm (mean 3.1 +/- 0.7) and late diastolic forward flow ranged from 1 to 3.6 cm (mean 2.1 +/- 0.7). Duration of early diastolic forward flow ranged from 161 to 256 ms (mean 187 +/- 29) and late diastolic forward flow ranged from 82 to 188 ms (mean 133 +/- 29). Data analysis for age indicated no significant difference in these measurements between children three to nine years old (n = 33) and children 9.1 to 18 years old (n = 27). The effect of respiration was observed in 10 randomly chosen subjects (mean age 8.6 +/- 4.1 years). Although early and late diastolic peak forward flow velocities, flow velocity integrals and flow duration during inspiration tended to be larger than during expiration, only late diastolic peak forward flow velocities during inspiration were significantly larger than during expiration (24.2 +/- 3.2 versus 18.2 +/- 3 cm/s, p = 0.001). This study defines normal Doppler ultrasound pulmonary arterial flow velocities, flow velocity integrals and flow duration during diastole in normal children. These results can be used for comparison with patterns found in disease states.