It is unclear how often patients with very mild aortic stenosis (gradients < 25 mmHg) need interval follow-up. The purpose of this study was to define the determinants of disease severity progression and to propose appropriate management strategies. It is known that congenital aortic stenosis is a progressive disease that requires long-term follow-up at consistent intervals. We studied 89 patients with very mild aortic stenosis. Cox proportional hazard modeling was performed to ascertain predictors of morbidity and mortality. Events were defined as valve surgery or death. Of the original 89 patients, 7 died (92% survival); one death was sudden and unexplained and six were noncardiac. Eighteen individuals were lost to follow-up (10 not located and 8 refused participation). Twelve (17%) had valve surgery. The minimum time interval between initial diagnosis of very mild aortic stenosis and surgery was 4.6 years (mean, 14.0). Age at diagnosis, gender, initial gradient, initial gradient/age, and aortic regurgitation were found not to be predictive of outcome. However, the slope of the transaortic gradient [change of gradient/time (years)] was predictive of outcome (hazard ratio of 1.69; confidence interval, 1.4-2.2). At least 17% of these patients progress to require operation. For patients with a gradient slope < 1.1, evaluation every 4 or 5 years is recommended. For patients with a gradient slope > 1.2, evaluation every 1 or 2 years seems prudent.