To determine the frequency of valvular regurgitation, 174 children from birth to 18 years old (mean age 7.42+/-4.54 years), with structurally normal hearts were analyzed. Flow patterns across the four valves were examined by pulsed- (PW), continuous-wave (CW) and color Doppler. Regurgitation was detected in 59.7% of the valves. Tricuspid regurgitation (TR) was most commonly found in 32.8% (n=57), pulmonary regurgitation (PR) in 17.2% (n=30), mitral regurgitation (MR) in 8.6% (n=15), and aortic regurgitation (AR) in 1.1% (n=2). The range of peak velocities of the regurgitant flow with CW were as follows: TR:0.98-2.54 m/sec, PR:0.50-1.80 m/sec, MR:0.72-2.30 m/sec, and AR:1.22-1.25 m/sec. The mean peak velocities of the regurgitant flow were similar with CW and PW measurements (p>0.05). The length of the regurgitant flow with color Doppler was less than 1 cm beyond the mitral and aortic valves. It reached up to 1.8 cm behind the pulmonary and 1.83 cm behind the tricuspid valves. Frequency of valvular regurgitation was unchanged with age (p>0.05). Tricuspid regurgitation was more frequent in males (40.9% versus 23.5%; p=0.016). Regurgitation of tricuspid, pulmonary or mitral valves is relatively common in children with structurally normal hearts. Aortic regurgitation is scarce and the possible pathologic cause should always be carefully sought.