OBJECTIVES: The objective was to assess the prevalence and patterns of modafinil and zolpidem use among emergency medicine (EM) residents and describe side effects resulting from use. METHODS: A voluntary, anonymous survey was distributed in February 2006 to EM residents nationally in the context of the national American Board of Emergency Medicine in-training examination. Data regarding frequency and timing of modafinil and zolpidem use were collected, as well as demographic information, reasons for use, side effects, and perceived dependence. RESULTS: A total of 133 of 134 residency programs distributed the surveys (99%). The response rate was 56% of the total number of EM residents who took the in-training examination (2,397/4,281). Past modafinil use was reported by 2.4% (57/2,372) of EM residents, with 66.7% (38/57) of those using modafinil having initiated their use during residency. Past zolpidem use was reported by 21.8% (516/2,367) of EM residents, with 15.3% (362/2,367) reporting use in the past year and 9.3% (221/2,367) in the past month. A total of 324 of 516 (62.8%) of zolpidem users initiated use during residency. Side effects were commonly reported by modafinil users (31.0%)-most frequent were palpitations, insomnia, agitation, and restlessness. Zolpidem users reported side effects (22.6%) including drowsiness, dizziness, headache, hallucinations, depression/mood lability, and amnesia. CONCLUSIONS: Zolpidem use is common among EM residents, with most users initiating use during residency. Modafinil use is relatively uncommon, although most residents using have also initiated use during residency. Side effects are commonly reported for both of these agents, and long-term safety remains unclear.