Policy initiatives increasingly emphasise the importance of breaking down organizational and professional barriers in order to achieve the delivery of effective mental health services. In this context, joint commissioning is seen as providing a way forward, and GPs are now identified as having a key role to play, alongside other professionals and agencies. However, there is evidence that joint commissioning is not yet well established, and a number of barriers to its development have been identified. The study reported here aimed to inform the development of joint commissioning between primary health care and social care in Wales by first mapping progress to date and then exploring the issues involved in more detail through three case studies. After the methods used for each stage have been described, the results are presented and discussed in relation to the problems identified and potential approaches to their resolution.