OBJECTIVE Despite valvular regurgitation being a common finding in children, its prevalence in infants is unclear. The aim of this study was to determine the presence and severity of valvular regurgitation in normal infants using echocardiographic screening. METHODS Two-dimensional (2D) color Doppler echocardiography was performed on 420 consecutive infants (aged 1-12 months) with structurally normal hearts. Pulsed, continuous-wave, and color Doppler imaging techniques were used to detect and evaluate regurgitant blood flow at each valve. RESULTS Valvular regurgitation was present in 258 infants (61.4%). Among these, 41 (15.9%) were found to have a heart murmur. Tricuspid regurgitation was found in 237 (56.4%) infants, pulmonary regurgitation in 71 (16.9%), mitral regurgitation in 51 (12.1%), and aortic regurgitation in nine (2.1%). Regurgitation of one valve occurred in 161 (38.3%) infants, of two valves in 84 (20%), and of three valves in 13 (3.1%). Right-sided regurgitation was significantly more common than left-sided regurgitation (p < 0.05). The degree of regurgitation was trivial or mild in 97.3% of infants and the peak velocities of the regurgitant jets were < or = 2.5 m/sec in all the valves, by Doppler echocardiography. CONCLUSIONS The prevalence of inaudible valvular regurgitation is high in infants with structurally normal hearts. Multiple-valve involvement with regurgitation is not uncommon. Mild severity and low velocity on color Doppler, and the structural information provided by 2D imaging strongly suggest that these regurgitant flows are physiologically normal in infancy.