We present a case of a patient scheduled for mitral valve replacement and possible aortic valve replacement. On Doppler examination, her peak transaortic pressure gradient measured on three separate occasions (pre-, intra-, and postoperatively) was approximately 60 mm Hg. In contrast, the peak-to-peak pressure gradient (cardiac catheterization) was 11 mm Hg. This latter gradient was confirmed in the operating room by direct simultaneous measurement of the pressures in the left ventricle and ascending aorta. Potential causes for this discrepancy are discussed, among which the "pressure recovery phenomenon" is considered the most important.