Background The role of three-dimensional transesophageal echocardiography (3 DTEE) vs multidetector computed tomography ( MDCT) in aortic annular sizing has been poorly defined in patients undergoing transcatheter aortic valve replacements ( TAVR). We set to determine the correlation between 3 DTEE and MDCT in measuring the aortic annulus prior to TAVR. Methods In an observational, retrospective study, we compared aortic annular areas measured by MDCT and 3 DTEE in TAVR patients. The aortic annular area was measured by planimetry of images obtained by MDCT pre- TAVR and by intra- TAVR TEE using 3D rendering of the aortic annulus followed by planimetry. Our primary outcome was degree of correlation between mean aortic annulus area by 3 DTEE and MDCT . Results Of the 111 consecutive patients undergoing TAVR who had measurements from both modalities available for comparison between February 2012 and April 2015, 87 met inclusion criteria. The mean aortic annular area by MDCT was 4.44±0.88 cm2 and by 3 DTEE was 4.33±0.78 cm2. There was a strong positive linear correlation between aortic annular area measurements obtained from these two modalities with mild relative underestimation by 3 DTEE (ρ=.833). This relationship can be estimated using the predictive formula: