Objectives:? The objectives were to determine the frequency of administration of potentially inappropriate medications (PIMs) to older emergency department (ED) patients and to examine recent trends in the rates of PIM usage. Methods:? The data examined during the study were obtained from the National Hospital Ambulatory Medical Care Survey (NHAMCS). This study utilized the nationally representative ED data from 2000?2006 NHAMCS surveys. Our sample included older adults (age 65 years and greater) who were treated in the ED and discharged home. Estimated frequencies of PIM-associated ED visits were calculated. A multivariable logistic regression model was created to assess demographic, clinical, and hospital factors associated with PIM administration and to assess temporal trends. Results:? Approximately 19.5 million patients, or 16.8% (95% confidence interval [CI] = 16.1% to 17.4%) of eligible ED visits, were associated with one or more PIMs. The five most common PIMs were promethazine, ketorolac, propoxyphene, meperidine, and diphenhydramine. The total number of medications prescribed or administered during the ED visit was most strongly associated with PIM use. Other covariates associated with PIM use included rural location outside of the Northeast, being seen by a staff physician only (and not by a resident or intern), presenting with an injury, and the combination of female sex and age 65?74 years. There was a small but significant decrease in the proportion of visits associated with a PIM over the study period. Conclusions:? Potentially inappropriate medication administration in the ED remains common. Given rising concerns about preventable complications of medical care, this area may be of high priority for intervention. Substantial regional and hospital type (teaching versus nonteaching) variability appears to exist. ACADEMIC EMERGENCY MEDICINE 2010; 17:231?237 © 2010 by the Society for Academic Emergency Medicine