To assess the prevalence and flow characteristics of valvular regurgitation detected by Doppler echocardiography in normal subjects, pulsed and continuous wave Doppler studies were performed in 100 adult volunteers without evidence of heart disease. Evidence of valvular regurgitation was present in 73% of subjects. There were 46 subjects with regurgitation of one valve, 24 with regurgitation of two valves and 3 with regurgitation of three valves. Right-sided regurgitation was significantly more common than was left-sided regurgitation (81 versus 22 valves, p less than 0.01). Regurgitant flow was never detected farther than 1 cm from the valve by pulsed Doppler study. Tricuspid regurgitation was detected in 50 subjects and was characterized by a holosystolic velocity signal; a complete spectral envelope was recorded in 32 subjects. The peak velocity of the regurgitant jet for this group was 1.7 to 2.3 m/s (mean 2.0 +/- 0.2). Thirty-one subjects were found to have pulmonary regurgitation with a peak velocity of 1.2 to 1.9 m/s (mean 1.5 +/- 0.2); no subject demonstrated regurgitant flow in early diastole. There were 21 subjects with mitral regurgitation; continuous wave Doppler signals were always of low intensity with a poorly defined spectral envelope and an absence of high velocities. Peak velocities ranged from 1.1 to 4.4 m/s (mean 2.3 +/- 0.9) and in 19 subjects were less than 3.5 m/s. The mean age of subjects with mitral regurgitation was significantly higher than that of subjects without mitral regurgitation (p = 0.01). Aortic regurgitation was detected in only one subject. This study provides further evidence that valvular regurgitation is frequently detected by Doppler echocardiography in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)