To study the incidence, outcome and potentially avoidable causes of inpatient cardiopulmonary arrests in a hospital with a "mature" rapid response system (RRS). Retrospective observational study of all cardiopulmonary arrest events in 2005. University of Pittsburgh Medical Center Presbyterian Hospital, a 730-bed academic, urban, tertiary care adult hospital in the USA. None. During the calendar year 2005, the 16th year since the establishment of a medical emergency team (MET)/RRS, the MET was activated 1942 times; 111 of these events were cardiopulmonary arrest events (3.26 arrest events/1000 patient admissions), and 1831 were non-arrest patient crisis events (53.8 crisis events/1000 patient admissions). A review of the 104 index cardiopulmonary arrest events revealed that 26 (25%) patients survived to discharge. Event survival decreased as the intensity of patient monitoring decreased (83% in intensive care units, 69% in monitored, and 36% in unmonitored units; p = 0.002), but the rate of subsequent in-hospital death was higher in the more intensely monitored settings (60%, 38%, 23%, respectively; p = 0.022). Nineteen (18%) arrests were deemed to be "potentially avoidable". Avoidable arrests were classified as: failure to adhere to established hospital patient care guideline or policy; inadequate monitoring or surveillance; or delays in dealing with patient needs including delay in MET/RRS activation. In spite of the high crisis event rate and a low rate of cardiac arrests, potentially avoidable cardiopulmonary arrests still occurred. According to the present study more cardiopulmonary arrest events might be avoided by better adherence to hospital patient care policies, by closer monitoring on floors and by preventing delays in addressing deterioration in patient condition.