This report discusses the involvement of drug users in making decisions about their treatment. User involvement has become a key principle in the delivery of health and social care services in the UK but is one that is not easily implemented in practice. This research, based on an in-depth investigation of drug service users' and practitioners' experiences of user involvement in specialist treatment agencies, explores a range of related issues, including: "The nature and extent of user involvement "The desire for involvement amongst practitioners and service users"Likely constraints on involvement"The impact and relative importance of involvement on treatment outcomes The report concludes with recommendations for facilitating user involvement in drug treatment decision-making.