It has been estimated that 11% of United States ED patients have substance use disorder. One urban ED estimated that nearly 7% of visits were due to illicit drug use. In a large statewide review of ED visits, alcohol use disorder was more prevalent in rural settings while opioid use disorder was more prevalent in urban settings. Substance use leads to harmful outcomes such as acute injuries, overdose, and medical complications. Forensic laboratory data offers some insight on which drugs are commonly used in US cities. (Ethanol is not included in these reports, but is used ubiquitously and considered to be the most commonly used intoxicating drug.) Opioids, sympathomimetics, cannabinoids, and sedatives classes predominate in all US cities, although there is some regional variation of the specific drugs used among cities. In Baltimore, for example, the top four drugs identified are cocaine, fentanyl, heroin, and tramadol; in Phoenix, the top four are cannabis, fentanyl, heroin, and methamphetamines.