For most countries annual health expenditures are increasing. According to the World Health Organization (WHO), in 2011, Brazil expends about 10 percent of its gross domestic product on health. Hence, improving health care efficiency is becoming increasingly important. Within a hospital, the Operating Rooms represent a major cost and incomes center. Operating Rooms are a difficult aspect to manage because many stakeholders involved in the process, namely, patients, surgeons, staff, hospital manager, and the scarcity of resources like beds, operating rooms, especial equipment, etc. This dissertation deals with a real problem of operating rooms programming for elective patients in a Lisbon hospital. For this problem, we propose a reformulation of the integer programming model proposed by Marques et al. (2012). This reformulation is based on the knapsack problem, in order to find a more efficient solution in terms of time. According to tests carried out, a reformulation in the model that breaks symmetry, computationally provides a more efficient solution and enhance the original solution because it reduces the initial gap from 782.59 percent to 2.25 percent. In addition, a simulation model was proposed to create various scenarios to assess the involved uncertainty, mainly due to surgery duration variation. This simulation can serve as a support tool in decision-making, according to the degree of conservatism of the decision maker, Operating Rooms scheduling policies can be established.