An increasing number of cities worldwide use surveillance cameras to prevent crime, but little is known about whether these cameras reduce crime or simply move it to other locations. This column studies the impact of a large-scale introduction of police-monitored cameras in Montevideo, Uruguay. The findings indicate a 20% reduction in crime in areas of the city where the cameras are located, with no evidence of a displacement effect. The programme also appears to offer value for money compared with other security and crime prevention measures.