National community health worker (CHW) programmes supported by Ministries of Health have been introduced in a number of countries as part of their primary health care policy. Although in many of these programmes the CHWs are salaried or receive an honorarium, there are a number of large-scale programmes in which CHWs work as unpaid volunteers. This paper looks at one such programme in Sri Lanka, in order to understand the motivation of such volunteers and to consider the feasibility of relying on volunteers to support primary health care policies. The lessons from the Sri Lanka case are generalized to other studies. The conclusion is that large-scale community level volunteer programmes will be characterized by high attrition and low activity rates and will only be sustainable under particular enabling conditions.