This review evaluates the effectiveness of local opinion leaders in improving professional practice and patient outcomes. It includes 18 randomized controlled trials involving over 296 hospitals and 318 primary care providers. The main findings show that using opinion leaders compared to no intervention resulted in a 12% absolute increase in compliance with desired practice. Opinion leaders alone compared to a single intervention showed a 14% increase, while opinion leaders combined with additional interventions showed a 10% increase. When opinion leaders were part of multiple interventions compared to no intervention, there was also a 10% increase. The effectiveness varied across studies, with some showing a 72% increase in compliance and others a 15% decrease. The review highlights that the role of opinion leaders was not consistently described, making it difficult to determine the best approach for optimizing their effectiveness. The results suggest that opinion leaders alone or in combination with other interventions may successfully promote evidence-based practice, but the effectiveness varies both within and between studies. The review also notes that the use of different methods to identify opinion leaders and the educational methods used by opinion leaders may influence their effectiveness. Overall, the evidence is heterogeneous, with varying study designs, settings, and outcomes. The review concludes that further research is needed to better understand the best ways to use opinion leaders to improve professional practice and patient outcomes.This review evaluates the effectiveness of local opinion leaders in improving professional practice and patient outcomes. It includes 18 randomized controlled trials involving over 296 hospitals and 318 primary care providers. The main findings show that using opinion leaders compared to no intervention resulted in a 12% absolute increase in compliance with desired practice. Opinion leaders alone compared to a single intervention showed a 14% increase, while opinion leaders combined with additional interventions showed a 10% increase. When opinion leaders were part of multiple interventions compared to no intervention, there was also a 10% increase. The effectiveness varied across studies, with some showing a 72% increase in compliance and others a 15% decrease. The review highlights that the role of opinion leaders was not consistently described, making it difficult to determine the best approach for optimizing their effectiveness. The results suggest that opinion leaders alone or in combination with other interventions may successfully promote evidence-based practice, but the effectiveness varies both within and between studies. The review also notes that the use of different methods to identify opinion leaders and the educational methods used by opinion leaders may influence their effectiveness. Overall, the evidence is heterogeneous, with varying study designs, settings, and outcomes. The review concludes that further research is needed to better understand the best ways to use opinion leaders to improve professional practice and patient outcomes.