Aims: Description of a study protocol to analyze the effectiveness of the sequential implementation of a Rapid Response System (RRS) on the incidence of the composite endpoint of cardiac arrest, unplanned ICU admission, and mortality rates. Study Design: The COMET trial is a before-after, non-randomized multi-center trial. Place and Duration of Study: The COMET trial was held in the Netherlands in fourteen Dutch hospitals from April 2009 until November 2011. Each hospital included two surgical and two general medicine nursing wards. Methodology: Prior to the introduction of the RRS, endpoints were collected for 5 months as part of a baseline assessment. The RRS was introduced in two steps. Initially, two tools were introduced during 7 months for early detection of the deteriorating patient: the Modified Early Warning Score (MEWS) and for structured communication, the Situation-Background-Assessment-Recommendation (SBAR) tool. During the next 15 months the Rapid Response Team (RRT) was operational in addition ...