We determined the sequential hemodynamic changes after percutaneous aortic balloon valvuloplasty by means of two-dimensional and Doppler echocardiographic examinations in 25 patients immediately before, immediately after, and 24 to 36 hours after valvuloplasty. An aortic valve area was determined at all three time periods by using the continuity equation from the Doppler velocity profiles. The aortic valve area by Doppler echocardiography immediately before valvuloplasty correlated with that determined by cardiac catheterization (r = 0.85, SEE = 0.08 cm2). The mean aortic valve gradient by Doppler echocardiography was 50 +/- 22 mm Hg before the procedure, decreasing to 29 +/- 12 mm Hg (P less than 0.001), with a small, but significant, increase 1 day later to 33 +/- 13 mm Hg (P less than 0.001). The mean subvalvular velocity increased from 0.44 +/- 0.13 to 0.52 +/- 0.15 m/sec immediately after valvuloplasty (P less than 0.001), increasing further to 0.60 +/- 0.16 m/sec 1 day later (P less than 0.001). The resultant aortic valve area increased from 0.45 +/- 0.11 to 0.73 +/- 0.18 cm2 immediately after (P less than 0.05). One day later, the aortic valve area increased further to 0.86 +/- 0.19 cm2 (P less than 0.05). Because of the dynamic changes occurring during the first 24 to 36 hours after balloon valvuloplasty, hemodynamic measurements taken immediately after the procedure may underestimate the efficacy of this technique.