In this chapter, the authors present a formal model of the Anesthesia Unit and Surgical Wards (UAPQ) of a Chilean hospital. The objective was to document and to understand its operation, to assist hospital management and to facilitate its simulation. The model was built with Specification and Description Language (SDL). This methodology was used because it allows the design of a model that represents the system in a graphical, modular, and standard way. Our design contains the following agents: the system, 11 blocks, and 52 processes. The blocks and the processes describe the clinical and administrative activities. The environment of the UAPQ model contains 3 components: clinical services, emergency units, and support units. © 2014, IGI Global.