Simple SummaryFree-roaming dogs in Greater Bangkok are tolerated and fed by sympathetic citizens. Although many people accept dogs on their street, many more are not accepting of the situation and there are concerns about dog welfare, nuisance behaviors and the ever-present risk of rabies transmission. Catch, Neuter, Vaccinate and Return (CNVR) is an intervention that catches unowned dogs, and collects owned roaming dogs from their owners, for surgical sterilization, vaccination and then return. This prevents these free-roaming dogs from breeding and provides them immunity from rabies. An evaluation of a 5-year CNVR intervention in Greater Bangkok found a reduction in free-roaming dog density, a reduction in dog rabies cases and an improvement in dog-human relationships. Although CNVR was successful at reducing breeding by the current free-roaming dog population, we found evidence that free-roaming dogs are coming from other sources, presumably from abandoned or lost owned dogs. Hence a fully effective dog population management program will require interventions that target abandonment and loss of owned dogs in addition to CNVR.AbstractA high-intensity catch, neuter, vaccinate and return (CNVR) intervention was used over 5 years to manage the free-roaming dog population of Greater Bangkok, using nearly 300,000 CNVR operations across six provinces. An evaluation was conducted using multiple methods to assess the impact of this intervention, including clinical data, an observational street survey, an online attitude survey and reported cases of dog rabies confirmed with laboratory testing. The evaluation found evidence of a reduction in free-roaming dog density over time (24.7% reduction over 5 years), a reduction in dog rabies cases (average reduction of 5.7% rabies cases per month) and an improvement in dog–human relationships (a 39% increase per year in free-roaming dogs with visible signs of ownership or care and a perception of less trouble with free-roaming dogs in districts benefiting from CNVR). The CNVR intervention appears to have been effective at reducing the current free-roaming dog population and minimizing one future source of free-roaming dogs by limiting breeding of dogs accessible on the streets. However, there is evidence that other sources of free-roaming dogs exist, presumed to be predominately abandoned or lost owned dogs that were previously inaccessible to the CNVR intervention because they were ordinarily confined or living outside the project area. Hence, fully effective dog population management will require further interventions targeting owned dogs in addition to this CNVR effort.