The aim of the thesis was to gain insight into the effect of a rapid response system (RRS) on cardiac arrests and/or unexpected deaths and on unplanned ICU admissions in surgical patients. In addition, we aimed to gain insight into the effect of a multifaceted implementation strategy on adherence of the ward staff to the afferent RRS procedure. Lastly, we assessed the effects of an RRS on health-related quality of life (HRQOL) and on hospital costs. Results We were unable to show a significant positive effect of an RRS on the incidence of cardiac arrest and/or unexpected death, nor on HRQOL. We found that implementation of an RRS increased hospital costs, which were to a large extent caused by the increased number of unplanned ICU admissions after RRS implementation. However, we cannot conclude that introduction of an RRS is ineffective for several reasons. First, the low baseline incidence of cardiac arrest and/or unexpected death made it very difficult to prove a significant reduction in these outcomes in the surgical ward of our hospital. Second, implementation was likely suboptimal since half of the unplanned ICU admissions were not preceded by a medical emergency team (MET) consultation. Our scenario analysis suggests that costs can be lowered, provided earlier MET calls lead to earlier unplanned admissions to the ICU, resulting in a shorter length of stay in the ICU and lower costs. Implications for clinical practice and further research To achieve earlier MET calls further implementation strategies are needed. Continuous evaluation with the use of the outcome parameter ‘number of ICU days per 1000 patient-days’ may be more helpful to gain insight into the effectiveness of an RRS on a particular ward. © 2015, Netherlands Society of Intensive Care. All rights reserved.