More than one million people are killed worldwide each year in traffic crashes. Driving after drinking alcohol increases the chance of a traffic crash. To reduce alcohol-impaired driving, some police agencies have increased the number of police patrols or the time the police spend patrolling. The aim of these increased patrols is to raise the perceived and actual likelihood that impaired drivers will be identified and stopped. Identification is based on observable behavioral cues, which include moving violations, erratic driving, and crash involvement. In response to these cues, police officers stop the driver and administer tests for alcohol impairment. We found 32 studies that tested the effects of increased police patrols on traffic deaths, injuries, and crashes. There was one randomized controlled trial and no quasi-randomized controlled trials. Almost all of the programs included additional interventions like community information programs, media campaigns, and special training for police officers. Most studies found that increased police patrols reduced traffic crashes and fatalities. Evidence for the effect on traffic injuries was less consistent. The detail provided on the methodology of included studies was almost uniformly poor. When this information was reported, the methodological quality was often weak. Therefore, the available evidence does not firmly establish that increased police patrols reduce the adverse consequences of alcohol-impaired driving. Good quality controlled studies with adequate sample size are needed to evaluate increased patrols. Also needed are studies assessing the cost-effectiveness of this intervention.