The Institute for Healthcare Improvement (IHI) has promoted implementing a RRS to provide safer care for hospitalized patients. Additionally, the Joint Commission made implementing a RRS a 2008 National Patient Safety Goal. Although mandated, the evidence to support the effectiveness of a RRS to reduce cardiac arrests on hospital medical or surgical floors and un-anticipated ICU transfers remains inconclusive, partly because of weak study designs and partly due to a failure of published studies to report all critical aspects of their intervention. This study attempted to evaluate the effectiveness and the implementation of a RRS on the two campuses of the UMass Memorial Medical Center (UMMMC). The first study presented was an attempt to identify the preventability and timeliness of floor to ICU transfers. This was done using 3 chief residents who reviewed 100 randomly selected medical records. Using Cohen’s kappa to assess the inter-rater reliability it was determined that 13% of the cases could have possibly been preventable with earlier intervention. The second study was an evaluation of the effectiveness of the Rapid Response System. Outcomes were cardiac arrests, code calls and floor to ICU admissions. There were two study periods 24 months before the intervention and 24 months after. A Spline regression model was used to compare the two time periods. Though there was a consistent downward trend over all 4 years there were no statistically significant changes in the cardiac arrests and ICU transfers when comparing the before and after periods. There was a significant reduction in code calls to the floors on the University campus. The third study was a modified process evaluation of the Rapid Response intervention that will assess fidelity of RRS implementation, the proportion of the intended patient population that is reached by the RRS, the overall number of RRS calls implemented (dose delivered) and the perceptions of the hospital staff affected by the RRS with respect to acceptability and satisfaction with the RRS and barriers to utilization. The process evaluation showed that that the Rapid Response System was for the most part being used as it was designed, though the nurses were not using the specific triggers as a deciding factor in making the call. Staff satisfaction with the intervention was very high. Overall these studies demonstrated the difficulty in clearly defining outcomes and data collection in a large hospital system. Additionally the importance of different study designs and analysis methods are discussed.