Many patients have physiological deterioration prior to cardiac arrest, death and intensive care unit (ICU) admission, that are detected and documented by medical and nursing staff. Appropriate early response to detected deterioration is likely to benefit patients. In a multi-centre, prospective, observational study over three consecutive days, we studied the incidence of antecedents (serious physiological abnormalities) preceding primary events (defined as in-hospital deaths, cardiac arrests, and unanticipated ICU admissions) in 90 hospitals (69 United Kingdom [UK]; 19 Australia and 2 New Zealand [ANZ]). 68 hospitals reported primary events during the three-day study period (50 United Kingdom, 16 Australia and 2 New Zealand). Data on the availability of ICU/HDU beds and cardiac arrest teams and Medical Emergency Teams were also collected. Of 638 primary events, there were 308 (48.3%) deaths, 141 (22.1%) cardiac arrests, and 189 (29.6%) unplanned ICU admissions. There were differences in the pattern of primary events between the UK and ANZ (P < 0.001). There were proportionally more deaths in the UK (52.3% versus 35.3%) and a higher number of unplanned ICU admissions in ANZ (47.3% versus 24.2%). Sixty percent (383) of primary events had a total of 1032 documented antecedents. The most common antecedents were hypotension and a fall in Glasgow Coma Scale. The proportion of ICU/HDU to general hospital beds was greater in ANZ (0.034 versus 0.016, P < 0.001) and medical emergency teams were more common in ANZ (70.0% versus 27.5%, P = 0.001). The data confirm antecedents are common before death, cardiac arrest, and unanticipated ICU admission. The study also shows differences in patterns of primary events, the provision of ICU/HDU beds and resuscitation teams, between the UK and ANZ. Future research, focusing upon the relationship between service provision and the pattern of primary events, is suggested.