Objective: The economic benefits of reducing emergency department (ED) crowding are potentially substantial as they may decrease hospital length of stay. Hospital administrators and public officials may therefore be motivated to implement crowding protocols. We sought to identify a potential cost of ED crowding by evaluating the contribution of excess ED length of stay (LOS) to overall hospital length of stay. Methods: We performed a retrospective review of administrative data of adult patients from two urban hospitals (one county and one university) in Brooklyn, New York from 2006-2007. Data was provided by each facility. Extrapolating from prior research (Krochmal and Riley, 2005), we determined the increase in total hospital LOS due to extended ED lengths of stay, and applied cost and charge analyses for the two separate facilities. Results: We determined that 6,205 (5.0%) admitted adult patients from the county facility and 3,017 (3.4%) patients from the university facility were held in the ED greater than one day over a one-year period. From prior research, it has been estimated that each of these patient’s total hospital length of stay was increased on average by 11.7% (0.61 days at the county facility, and 0.71 days at the university facility). The increased charges over one year at the county facility due to the extended ED LOS was therefore approximately $9.8 million, while the increased costs at the university facility were approximately $3.9 million. Conclusion: Based on extrapolations from Krochmal and Riley applied to two New York urban hospitals, the county hospital could potentially save $9.8 million in charges and the university hospital $3.9 million in costs per year if they eliminate ED boarding of adult admitted patients by improving movement to the inpatient setting. [West J Emerg Med. 2011;12(2):192-197.]