Models of Care should encourage a cohesive and collaborative response and the establishing of clear protocols, well-defined treatment modalities and care pathways and open systems of communication between individual professionals and service providers. Other models involve stronger liaison links between generic substance misuse and mental health services. Models of Care embraces a wide range of professions and professionals, and requires clear linkage with other, non-substance misuse specific services. Mark's story highlights some of the relationships and collaborative working that will be required. Mark might have had other problems associated with his injecting drug use: hepatitis or other blood-borne viruses, or HIV, are common. As Models of Care becomes fully implemented, it will be vital for care co-ordinators to develop a fuller, working appreciation of the contributions that different professionals can make to the process of treatment and care of individual drug users and those affected by their drug-using behaviours.