This publication reflects on and reinforces the lessons and experience of undertaking transboundary conservation programmes and sets out some existing and new guidance for those involved. It proposes a diagnostic approach to determining what the underlying purpose is for the transboundary initiative, and to guide the practitioner to respond to this purpose and need when the programme is designed and implemented. This advice is presented in the form of a very useful self-assessment tool developed from a suite of underlying case studies from pilot sites in the Dinaric Arc.