Every day, a hospital emergency roomface a number of that generates a negative effect in the patient flow. For Lean's approach, this disadvantages are called wastes, are classified in accordance to its type (confusion, movement, inventory, waiting, over-processing, reprocess and defects), and most of them are evitable. The methodology's application in healthcare offers a broader view of the problem, and enable the improvement ideas generation that can modify the patient flow, the communication processes, or even make structural changes. This project summarizes the experience in the Hospital Universitario de la Samaritana's emergency room, where several improvement strategies. As a result, the lead time was reduced in more than 30 minutes using short term strategies, and there was an increase in the percentage of activities that add value to the patient in most of the operations.