[영문]Abstract Objective: To investigate the prevalence of prescribing errors identified by pharmacists in hospital inpatients and the factors influencing error identification rates by pharmacists throughout hospital admission. Setting: 880-bed university teaching hospital in North-west England. Methods: Data about prescribing errors identified by pharmacists (median: 9 (range 4?17) collecting data per day) when conducting routine work were prospectively recorded on 38 randomly selected days over 18 months. Main outcome measures: Proportion of new medication orders in which an error was identified; predictors of error identification rate, adjusted for workload and seniority of pharmacist, day of week, type of ward or stage of patient admission. Results: 33,012 new medication orders were reviewed for 5,199 patients; 3,455 errors (in 10.5% of orders) were identified for 2,040 patients (39.2%; median 1, range 1?12). Most were problem orders (1,456, 42.1%) or potentially significant errors (1,748, 50.6%); 197 (5.7%) were potentially serious; 1.6% (n = 54) were potentially severe or fatal. Errors were 41% (CI: 28?56%) more likely to be identified at patient’s admission than at other times, independent of confounders. Workload was the strongest predictor of error identification rates, with 40% (33?46%) less errors identified on the busiest days than at other times. Errors identified fell by 1.9% (1.5?2.3%) for every additional chart checked, independent of confounders. Conclusions: Pharmacists routinely identify errors but increasing workload may reduce identification rates. Where resources are limited, they may be better spent on identifying and addressing errors immediately after admission to hospital.