Guidelines for reporting echocardiographic studies in prosthetic heart valve patients have recently been published. Prothesis-patient mismatch (PPM) was first described in 1978 and is present when the effective orifice area (EOA) of an implanted surgical prosthetic valve is too small in relation to a patient’s body surface area (BSA). PPM remains a common occurrence and has been reported in the literature in up to 20-70% of AVR patients. This is concerning, since undersized prostheses relative to body size may result in higher transprosthetic gradients, worse hemodynamic function and adverse patient outcomes. We examined reporting trends in patients with prosthetic aortic and mitral valves at London Health Sciences Centre (LHSC)and St Joseph's Health Care, with particular focus on PPM in these patient populations. Patients with prosthetic aortic valve replacement (AVR) and/or mitral valve replacement (MVR) undergoing echocardiography between September 2003 and August 2013 were identified. Studies with complete patient data for whom PPM could be measured were included for further analysis. PPM was defined as EOA/BSA ≤ 0.85 cm2/m2 in the aortic position (0.65-0.85 cm2/m2 moderate, <0.65 cm2/m2 severe), and as ≤ 1.3 cm2/m2 in the mitral position. Demographic and echocardiographic parameters were evaluated. Overall 8901 studies from 3378 patients were identified (61% male; mean age 68 ± 13 years). Echocardiographic studies (mean 2.6 studies/patient) were performed in patients with AVR (6290, 71%), MVR (1904, 21%) or both (707, 8%). Complete data sets were obtained for 2391 AVR studies. PPM was present in 44% of AVR studies (severe in 3%). AVR patients with PPM were older at the time of valve replacement (71 vs. 63 years) and at follow-up (73 vs. 65 years), had greater body weight (86 vs. 81kg), larger BSA (1.97 vs. 1.92kg/m2), smaller left ventricular dimensions (47 vs. 49mm), LVOT (19 vs. 20mm) and aortic roots (30 vs. 32mm), with higher transprosthetic gradients (34 vs. 26mmHg) and lower Doppler velocity index (0.41 vs. 0.44) in comparison to patients without PPM (p<0.001 for all). PPM was more common in females (48% vs. 41%, p=0.002), in those with bioprosthetic AVR (56% vs. 9%, p<0.001), with concurrent CABG (52% vs. 39%, p<0.001) and without concurrent aortic root enlargement surgery (46% vs. 32%, p<0.001). The presence of PPM in AVR patients in our study population was common. Our data analysis identified patient subsets with a higher prevalence of PPM, which co-localized with indices of impaired cardiac performance.