Background: STOPP/START was formulated to identify potentially inappropriate prescribing (PIP) and potential prescribing omissions (PPOs) in older people. The purpose of this study was to determine the prevalence of PIP and PPO in older Irish patients in residential care using STOPP/START.Methods: data were collected prospectively from seven publicly funded nursing homes within the Munster Region of Ireland over 3 weeks. Data recorded included: current medication, current medical conditions, previous medical conditions, biochemistry, sex and age. STOPP/START was applied to each patient record.Results: of the 313 patients recruited, 74.4% (233) were female, mean age (±SD) 84.4 (±7.5) years. The total number of medicines prescribed was 2,555 [range: 1–16; median: 8 (IQR 6–10 )]. STOPP identified 329 instances of PIP in 187 (59.8%) patients and START identified 199 PPOs in 132 (42.2%) patients. The number of medicines prescribed was positively associated with PIP identified by STOPP (rs = 0.303, P < 0.01). Age, sex and the number of medicines prescribed were not associated with prescribing omissions using START.Conclusions: a high proportion of patients recruited were prescribed at least one potentially inappropriate medicine, or had an omission of a clinically indicated medicine. Incorporating these tools into every-day practice could play a pivotal role in improving prescribing in this cohort.