Recent research data indicate a cause-and-effect relationship between inappropriate prescription medicines and serious ADEs in older people in hospital. To date, Beers' criteria have been the dominant set of criteria for defining potentially inappropriate medicines (PIMs) in late life. Research data collected by this group show that the recently validated STOPP/START criteria (Screening Tool of Older Persons' Prescriptions and Screening Tool to Alert doctors to Right Treatment) identify ADEs that are causal or contributory to acute hospital admission in older people 2.7 times more frequently than Beers' criteria. Based on these findings, our hypothesis is that STOPP/START criteria have the potential to be used as a regular intervention for the purpose of ADE prevention in older people. A recent single centre randomised control trial (RCT) undertaken at Cork University Hospital showed that prospective application of STOPP/START criteria led to a highly significant improvement in medication appropriateness in older hospitalised patients compared with standard inpatient pharmaceutical care. Significantly, the improvement in medication appropriateness was maintained to the end of the study follow-up i.e. 6 months post-discharge. However, the ability of STOPP/START criteria to significantly reduce ADEs in a prospective RCT has yet to be demonstrated.