Rapid response systems (RRS), implemented to treat the clinically deteriorating patient, have now been well studied, including studies examining their impact on cardiac arrests, mortality, and even end-of-life care. This observational cohort study compared the use of and outcomes from medical emergency teams (MET) 5 years after their implementation to those found at the time of initiation. The study found fewer unplanned ICU admissions and MET activation delays in experienced systems, suggesting that RRS may need to mature before their full impact is felt. This finding adds to the ongoing debate about and tension regarding the impact of RRS. A past AHRQ WebM&M perspective discussed early lessons from rapid response team implementation.