This paper is concerned with how poor populations can obtain access to trusted, competent knowledge and services in increasingly pluralistic health systems where unregulated markets for health knowledge and services dominate. The term "unregulated" here derives from the literature on the development of markets in low income countries and refers to the lack of state enforcement of formal laws and regulations. We approach this question of access through the changing roles and fortunes of community health workers over the last few decades and ask what kind of role they can be expected to play in the future. Community based health agents have been used in many settings as a way of filling gaps in service provision where more skilled personnel are not available. They have also fulfilled a more transformative role in broad based community development. We explore the reasons for the decline of programmes from the 1980s onwards. Using the specific experience of Bangladesh, the paper considers what lessons can be learned from past successes and failures and what needs to change to meet the challenges of 21st century health systems. These challenges are those of establishing credibility and legitimacy in a pluralistic environment and creating a sustainable livelihood strategy. The article concludes with a discussion of four potential models of community based health agents which are not necessarily exclusive: a generic agent that is closely linked to a reputable supervisory agency; a specialist cadre working with particular health conditions; an expert advocate; and a mobiliser or facilitator who can mediate between users and health markets.