The purpose of this investigation was to use Doppler echocardiography to evaluate respiratory problems significant enough to warrant supplemental oxygenation in newborn infants. Of 17 infants (mean gestational age 37.5 weeks, mean birth weight 3070 g) 14 (82%) had detectable tricuspid regurgitation. By modified Bernoulli equation, all infants had right ventricular pressure greater than 60% of systemic pressure, and nine of 14 had estimated right ventricular pressure at or near systemic pressures. In eight infants for whom sequential evaluations could be obtained, right ventricular pressure as a percentage of systemic pressure gradually decreased, and corresponded to decreasing needs for supplemental oxygenation. Tricuspid regurgitation could no longer be detected between 3 and 16 days after the first study, and was associated with decreased right ventricular pressures (less than 50% systemic) and weaning from supplemental oxygenation. We conclude that in the near-term infant with early respiratory difficulties, tricuspid regurgitation is common and is associated with increased right ventricular pressure.