General practice is a principal point of access for individuals who experience problems associated with cannabis use, including dependence on the drug. However, there are no clear guidelines on advice or clinical interventions for primary care practitioners regarding this area. Whilst it has been suggested that specific services to deal with cannabis users are required (Stephens et al., 1993) we have neither a clear idea of how many individuals in local populations may need support to give up or reduce cannabis use, nor of the knowledge or practice of GPs in relation to patients that use cannabis. This study examined GPs’ knowledge of cannabis-related harm, and their own responses and practice in treating patients who present for help. A postal questionnaire was sent to 155 general practitioners in Wandsworth, of which 97 (63%) completed questionnaires were returned. The results showed that GPs in Wandsworth are aware of the risks associated with cannabis use, and are also motivated to improve their knowledge base. Attitudes towards the appropriate setting and approach to treatment interventions were mixed, with some believing that cannabis users could be treated in primary care and others preferring onward referral to specialist drug ser-vices. However, given that 46% (n = 47) of our sample had been approached by a patient wishing to stop using cannabis, effective primary care interventions are required. The study argues for improved primary care engagement with cannabis users seeking support via clear guidelines and training of practitioners, improved signposting to specialist services and shared care, and further consideration of issues around the recording of information relating to cannabis use. In addition, more national and strategic clarity regarding the potential harm of using cannabis, as well as treatment options and care pathways would be welcomed.