Driving Under the Influence (DUI), also known as driving while intoxicated (DWI), drunk driving, or impaired driving, refers to a conduct, which arise in the area of traffic, when the driver of a motor vehicle has consumed a certain amount of alcohol or drugs, including medicines. This consumption interfers and deteriorates the processes involved in driving as attention, sense, perception, decision-making and execution. So, it increases likelihood of experiencing a traffic accident. The consumption can be detected/measured to determine its presence/level by different methods and devices, in the first instance by law enforcement officers in checkpoints. It is considered a serious criminal offence against road safety under laws in certain countries. Depending on some factors, law from different countries, this behavior shall be punished by specific heavy penalties (civil or penal). Given the prevalence, incidence and tragic consequences of DUI, this kind of crime is more relevant than other offences. This entry reviews road traffic injuries as a public health concern, DUI as a major risk factor for road traffic injuries, Effects of DUI, Strategies to reduce/prevent DUI and Methods used by enforcement to detect DUI.