[영문]Motivational Interviewing (MI) is a client-centred, directive counselling method. This study evaluates the effectiveness of a two-day workshop in MI for forty social workers in changing self-reported practice over a three-month period, the levels of skills achieved, and factors associated with acquired skills, including the impact of post-workshop supervision. The focus of training was alcohol misuse but participants were encouraged to explore the use of MI with other issues. A multi-method pre and post-design was used, utilizing both quantitative and qualitative data and employing an embedded randomized controlled trial of the impact of supervision. The two-day workshop had a modest positive impact on evaluations of simulated practice, on some measures of attitudes to working with problem drinkers and in qualitative accounts of practice. Despite this, three months post-workshop, workers generally had not reached a skilful level of MI practice as measured in ratings of an interview with a simulated client. Offer of post-workshop supervision had little impact on skill, with take-up being low. There was a significant difference between participants in the two workshops, despite identical programmes and trainers. Qualitative data suggested that participants had found the training useful and many reported a positive impact on their practice.