The airway is the portal of entry for oxygen into the human body. Establishing an airway is the first priority of resuscitation because, without an adequate airway, all other medical treatments are futile. All airways established in the out-of hospital setting must be considered difficult airways; the importance of knowing when to intubate and what to do in the case of a technically challenging airway is not often appreciated. Several recent studies have highlighted the high failure rate for prehospital intubations as well as significant complications with this procedure. The most devastating is unrecognized esophageal intubation. In this chapter, we will briefly review some basic principles of airway assessment and the approach to tracheal intubation.