The probation service’s venture into financial partnerships with non-statutory agencies during the 1990s was viewed both as a development opportunity for improving services, and as a threat to professional identity and job security. Judith Rumgay studies partnership development with particular focus on programmes for substance misusing offenders. She explores tensions between probation and voluntary organizations, identifies features common to successful partnerships, and compares partnership arrangements with in-house specialist projects. She argues that the partnership enterprise touches the heart of the probation service’s mission in local communities.