BACKGROUND: Calcific aortic stenosis (AS) is the most common underlying pathology in patients undergoing heart valve surgery, with an expected increasing prevalence among the aging population. METHODS AND RESULTS: We identified the temporal trends in referral patterns, disease severity, and associated surgical risk among patients with AS between January 1, 1995 and December 31, 2012 at the Duke University Hospital. A total of 6103 patients had a finding of mild (n = 3303), moderate (n = 1648), or severe AS (n = 1152) in a native aortic valve. Overall presence of severe AS increased significantly over time (P = 0.009) with the most substantial increase occurring from 2010 and onward. Median age upon referral (P < 0.001) and attendant predicted surgical risk (P < 0.001) increased significantly in the observation period among patients with a finding of severe AS. Among patients with a finding of severe AS, the proportion of patients aged older than 80 years increased to 51.0% in the most recent time period (2010-2012) compared with 32.6% in the preceding time period (P < 0.001 for overall time trend). Similarly, the proportion of patients with a logistic EuroSCORE greater than 20% increased to 21.3% (2010-2012) from 12.1% (pre-2010). CONCLUSIONS: Among patients referred for echocardiography to a high-volume tertiary hospital center, a significant increase in the prevalence of severe AS was observed over time. This trend occurred in parallel with increasing age and predicted surgical risk at referral. Health-care resource planning should account for an increasing number of patients in need of high-risk aortic valve replacements in the near future.