There are three broad types of co-therapy or multiple therapy as it is sometimes called. The first consists of two therapists working together 'in vivo' with the family group; second, a team of therapists working together, one of whom is directly involved with the family in the therapy room while the others, although equally committed as therapists to the family, work from behind an observation screen; third, a team of therapists who work in different combinations with a family, intensively over a short period of time, as in multiple impact therapy.