This paper argues that workshop co-facilitators should be actively involved in planning, conducting and debriefing the workshops in which they are involved. The paper discusses 12 possible roles for workshop co-facilitators and attempts to motivate some of these roles with reference to Humanistic Psychology, Social Interdependence Theory, Socio-Cultural Theory and Social Constructionism. The co-facilitator roles are planning the workshop, befriending participants and facilitators, providing general and technical assistance, modelling behaviours and tasks, observing workshop processes, participating alongside participants, correcting and clarifying what facilitators have said and done, sharing their own and participants' ideas, assessing the workshop's effectiveness and understudying the facilitator. [This article was published in "Journal of Co-Operative Studies" v46 n2 p62-68 2013.]