Since the publication of To Err is Human, health care professionals have looked to high-reliability industries such as commercial aviation for guidance on improving system safety. One of the most widely adopted aviation-derived approaches is simulation-based team training, also known as crew resource management (CRM) training. In the health care domain, CRM training often takes place in custom-built simulation laboratories that are designed to replicate operating rooms or labor and delivery rooms. Unlike these traditional CRM training programs, in situ simulation occurs on actual patient care units, involves actual health care team members, and uses actual organization processes to train and assess team performance. During the past 24 months, our research team has conducted nearly 40 in situ simulations. In this paper, we present the results from one such simulation: a patient who experienced a difficult labor and delivery resulting in an emergency caesarean section and a hysterectomy. During the simulation, a number of latent environmental threats to safety were identified. The following article presents not only the latent threats but also the steps that the hospital has taken to remedy them. Results from clinical simulations in operational health care settings can help identify and resolve latent environmental threats to patient safety.