['Improving identification and treatment for substance use disorders is a national priority, but data about various drug use disorders encountered in emergency departments (EDs) are lacking. We examine past-year substance use and substance use disorders (alcohol, 9 drug classes) among adult ED users. Prevalences of substance use and substance use disorders among ED nonusers are calculated for reference purposes.', 'Using data from the 2007 to 2009 National Surveys on Drug Use and Health, we assessed substance use disorders among noninstitutionalized adults aged 18 years or older who responded to standardized survey questions administered by audio computer-assisted self-interviewing methods.', 'Of all adults (N=113,672), 27.8% used the ED in the past year. ED users had higher prevalences than ED nonusers of coexisting alcohol and drug use (15.2% versus 12.1%), drug use (any drug, 16.9% versus 13.0%; marijuana, 12.1% versus 9.7%; opioids, 6.6% versus 4.1%), and alcohol or drug disorders (11.0% versus 8.5%). Among substance users, the ED group on average spent more days using drugs than the non-ED group; ED users manifested higher conditional rates of substance use disorders than ED nonusers (alcohol or drugs, 15.9% versus 11.7%; marijuana, 16.6% versus 13.2%; cocaine, 33.2% versus 22.3%; opioids, 20.6% versus 10.0%; stimulants, 18.6% versus 9.2%; sedatives, 35.0% versus 4.4%; tranquilizers, 12.4% versus 5.2%). Regardless of ED use status, substance-using young adults, men, and less-educated adults showed increased odds of having a substance use disorder.'] Do alcohol and drug use disorders among adults in emergency department settings in the United States?