Using Doppler echocardiography, the prevalence of tricuspid and pulmonary valve regurgitation was determined prospectively in 173 normal children, aged 8.3 +/- 2.7 (range 5-14) years. Pulmonary regurgitation was defined as a red-yellow or mosaic coloured regurgitant flow, continuing to end-diastole with continuous-wave Doppler. It was found in 84% of the children. Tricuspid regurgitation was defined as a blue-green or mosaic coloured regurgitant flow from the tricuspid valve into the right atrium lasting > 0.5 systole, as determined by continuous-wave Doppler. Tricuspid regurgitation was present in only 8% of the children. Tricuspid regurgitation flow of very short duration, considered to be due to valve closure, was found in 75%. No effect of age, presence of a vibratory innocent heart murmur or gender on the prevalence of right-sided valvular regurgitation could be demonstrated. All regurgitations were haemodynamically insignificant. Thus right-sided valvular regurgitation in normal schoolchildren is a normal physiological finding with relatively high prevalence. In the absence of functional reasons for these regurgitations and in the absence of structural pulmonary or tricuspid valve disease, these signals should be considered physiological in order to avoid iatrogenic heart disease.