This study analyzes the various applications of Lean Methodologies in emergency departments (ED) from the years 2005 through 2010. These data were then used to create a predictive model that hospitals can use to assess the benefits of using lean within their ED. Metrics studied include 1) rate of patients that left the ED without being seen 2) length of stay and 3) overall patient satisfaction. These metrics were extracted from published studies and used to create a linear regression model, which could be applied to an ED to predict its status after implementing a lean project. After developing these formulas, they were applied to the ED of fictional hospital T-1 in order to predict benefit. After determining the approximate values for the post-lean metrics, an estimate of the financial benefit was developed in conjunction with a financial executive at Chandler Regional Medical Center, in Chandler, Arizona.