Although 1 of 10 nursing home residents is taking an antiepileptic drug (AED), no study to our knowledge has determined whether most residents are already receiving AED treatment when they are admitted or are given these drugs afterward. That differentiation was the focus of this study. The study group consisted of 10,318 residents, 65 years and older, admitted to 510 nursing homes located throughout the United States during the first quarter of 1999. AED prevalence at admission was 7.7%; three fifths had an epilepsy/seizure indication. In a multivariate analysis, factors associated with AED use at admission included epilepsy/seizure, bipolar depression, age group, and cognitive performance. In the follow-up cohort (N = 9,516), postadmission initiation of AEDs was 2.7%; one fifth had an epilepsy/seizure indication. In the multivariate analysis, factors associated with postadmission AED initiation included epilepsy/seizure indication, bipolar depression, age group, peripheral vascular disease, and cognitive performance. This rate of AED postadmission initiation within the first 3 months of admission was much higher than expected, suggesting that new symptoms may develop after admission. Results also show that the rate of AED use in nursing homes is not static.