WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: * Potentially inappropriate prescribing in older people is a well-documented problem and has been associated with adverse drug reactions and hospitalization. * Beers' criteria, Screening Tool of Older Persons' potentially inappropriate Prescriptions (STOPP) and Screening Tool to Alert doctors to Right Treatment (START) are screening tools that have been formulated to help physicians and pharmacists identify potentially inappropriate prescribing and potential prescribing omissions. * The prevalence of potentially inappropriate prescribing and prescribing omissions in the elderly population presenting to hospital with acute illness is high according to STOPP and START criteria. WHAT THIS STUDY ADDS: * Potential errors of prescribing and of omission of medicines are prevalent among medically stable older people in primary care. * Screening tools should be incorporated into the everyday practice of primary care doctors and community pharmacists as a means of preventing potential errors of prescribing commission and prescribing omission in older people. AIMS: Screening tools have been formulated to identify potentially inappropriate prescribing (IP) in older people. Beers' criteria are the most widely used but have disadvantages when used in Europe. New IP screening tools called Screening Tool of Older Person's Prescriptions (STOPP) and Screening Tool to Alert doctors to Right Treatment (START) have been developed to identify potential IP and potential prescribing omissions (PPOs). The aim was to measure the prevalence rates of potential IP and PPOs in primary care using Beers' criteria, STOPP and START. METHODS: Case records of 1329 patients >or=65 years old from three general practices in one region of southern Ireland were studied. The mean age +/- SD of the patients was 74.9 +/- 6.4 years, 60.9% were female. Patients' current diagnoses and prescription medicines were reviewed and the Beers' criteria, STOPP and START tools applied. RESULTS: The total number of medicines prescribed was 6684; median number of medicines per patient was five (range 1-19). Overall, Beers' criteria identified 286 potentially inappropriate prescriptions in 18.3% (243) of patients, whilst the corresponding IP rate identified by STOPP was 21.4% (284), in respect of 346 potentially inappropriate prescriptions. A total of 333 PPOs were identified in 22.7% (302) of patients using the START tool. CONCLUSION: Potentially inappropriate drug prescribing and errors of drug omission are highly prevalent among older people living in the community. Prevention strategies should involve primary care doctors and community pharmacists.