Volunteer community health workers (CHWs) are a key approach to improving community-based maternal and child health services in developing countries. BRAC, a large Bangladeshi non-governmental organisation, has employed female volunteer CHWs in its community-based health programs since 1977, recently including its Manoshi project, a community-based maternal and child health intervention in the urban slums of Bangladesh. A case-control study conducted in response to high dropout rates in the first year of the project showed that financial incentives, social prestige, community approval and household responsibilities were related to early retention in the project. This prospective cohort study seeks to better understand the factors associated with retention of volunteer CHWs once the project was more mature. The study concludes, factors that affect retention of CHWs may change over time, with some factors that are important in the early years of a project losing importance as the project matures. Community health programmes operating in fragile urban slums should consider changing factors over programme duration for better retention of volunteer CHWs.