Aims: To evaluate the effectiveness of opinion leaders for changing practitioners' behaviour; and determine how this strategy may be used to bridge the research-to-practice gap in the alcohol and drugs (AOD) field. Methods: A systematic literature review was undertaken to assess the use of opinion leaders for improving professional practice. Electronic databases, relevant websites, specialty journals and reference lists of included studies were searched systematically (1966-March 2005). Included studies were critically appraised according to level and quality of evidence and data on effectiveness of opinion leaders were extracted, tabulated and synthesized. Results: Four papers met the inclusion criteria for this review, including one existing systematic literature review comprising eight studies. Since no included studies were conducted in an AOD context, evidence was drawn from the broader medical and health fields. Overall, opinion leaders had variable effectiveness in changing professional practice. For the most part, studies lacked methodological quality and results were prone to bias. Conclusions: Despite good theoretical underpinnings for the use of opinion leaders to influence change in professionals' behaviour, current evidence of their effectiveness is sparse and inconsistent. There is a need for good quality, well-designed studies that are conducted in an AOD context using opinion leaders who are appropriately identified and adequately supported.