A flurry of research examining the effect of body-worn cameras (BWCs) on policing has arrived at mixed and inconclusive set findings. We present a multi-year study of the precinct rollout of BWCs in the New York City Police Department (NYPD), the largest metropolitan police force in the United States. Our study adds meaningfully to the prior body of work and begins to clarify some of the discord within it, particularly with respect to large urban police departments. We estimate the effect of BWC deployment on precinct volumes of citizen stops, arrests, complaints against officers and use-of-force incidents. Results indicate that BWCs lead to both significant increases in police stops of citizens, and significant decreases in arrests and citizen complaints. We find no significant change in the use of force by officers. We also document evidence of significant heterogeneity in the nature of stops and complaints. Our findings speak to at least three potential benefits of BWCs in urban law enforcement: (1) an increase in legitimate proactive policing; (2) a decrease in citizen complaints alleging that the police have abused their authority; and (3) a reduction in arrests (which appears to be beneficial regardless of whether the reduction is a result of modified behaviour on the part of police, citizens, or both).