BACKGROUND: Data suggest that patient-prosthesis mismatch (PPM) adversely effects late survival after aortic valve replacement (AVR). This study examined the incidence and implications of PPM in patients undergoing isolated AVR. METHODS: Prospectively collected data on patients undergoing isolated AVR for aortic stenosis between January 1, 1997 and December 31, 2007 were analyzed. The projected effective valve orifice area from in vivo data was indexed to body surface area (EOAi). PPM was defined as moderate for EOAi of <or = 0.85 cm(2)/m(2) and severe if <or = 0.6 cm(2)/m(2). The reference group comprised patients with EOAi > 0.85 cm(2)/m(2). The effect of PPM on postoperative survival was assessed by multivariate analysis. RESULTS: Of 801 patients, PPM was severe in 48 (6.0%), moderate in 462 (57.8%), and nonexistent in 291 (36.4%). Mismatch was associated with increasing age and female gender, thus resulting in an increase in the EuroSCORE (reference group, 4.9 +/- 2.6; moderate PPM, 5.8 +/- 2.4; and severe PPM, 6.1+/-2.1; p <0.001). PPM did not significantly increase hospital mortality. Four deaths occurred in the reference group (1.4%), 12 in the moderate PPM (2.6%), and none in the severe PPM group (p = 0.311). The 5-year survival estimates were 83% in reference, 86% in moderate PPM, and 89% in severe PPM (p = 0.25). By multivariate analysis, PPM was not an independent risk factor for reduced in-hospital or late survival. CONCLUSIONS: Moderate PPM is common in patients undergoing AVR for aortic stenosis, but severe mismatch is rare. Patients with PPM have similar early and late postoperative survival rate.