The Doppler echocardiographic indexes of the tricuspid and mitral valves were assessed in 74 normal subjects (35 women and 39 men, mean age 45 years). A reproducibility study was also performed to examine the various sources of technical and biological variability. There were significantly higher peak early and late flow velocities across the mitral valve than across the tricuspid valve (0.67 +/- 0.13 and 0.47 +/- 0.12 vs 0.51 +/- 0.08 and 0.35 +/- 0.09 m.s-1, respectively; all p less than 0.0001). There was no significant difference between the early:late (E:A) velocity ratios of the 2 valves (1.65 +/- 0.73 vs 1.75 +/- 0.67, p less than 0.01). There was a steeper mitral early deceleration slope (-3.59 +/- 1.07 vs -2.95 +/- 0.91 m.s-2) but no significant difference in pressure half-times across the 2 valves (47 +/- 7 vs 51 +/- 12 ms, p less than 0.1). No influence of gender or body surface area could be demonstrated. There was a weak but significant relation between mitral peak early, peak atrial velocity and E:A ratio and age (r = -0.39, p less than 0.001, r = 0.23, p less than 0.01, and r = -0.245, p less than 0.01, respectively). There was no significant correlation between any of the tricuspid flow parameters and age. Respiration caused pronounced variability in the tricuspid Doppler indexes and all tricuspid flows were sampled and analyzed only during inspiration. The intra- and interobserver variabilities were small for all of the Doppler indexes measured, but the day-to-day variability was quite significant especially for the pressure half-time, deceleration and acceleration slope values.(ABSTRACT TRUNCATED AT 250 WORDS)