This paper makes a contribution to a much-neglected aspect of policy analysis: the practice of power in implementation. Practices of power are at the heart of every policy process, yet are rarely explicitly explored in the health policy literature. This paper provides a detailed study of micro-practices of power by those at the frontline of service delivery in the implementation of a national community health worker policy in one rural South African sub-district. The paper is based on a small-scale qualitative study which collected data through observations, interviews and focus group discussions with health services and facility managers, community health workers and community members. Practices of power were analysed using VeneKlasen and Miller's categorization of multiple dimensions of power, as power over, power with, power to and power within. Furthermore, the concept of 'actor interface analysis' allowed exploration of different actors' experience, interests and their specific location in the landscape of local health system governance. The study revealed that almost all policy actors exercised some form of power, from authoritative power, derived from hierarchy and budget control, to the discretionary power of those working at lower levels to withhold labour or organize in-service training. Each of these practices of power had their rationale in different actors' efforts to make the intervention 'fit' their understandings of local reality. While each had a limited impact on policy outcomes, their cumulative effect produced a significant thinning down of the policy's intent. However, discretionary power was not always used to undermine policy. One manager's use of discretionary power in fact led to a partial reconstruction of the original policy intent. The paper concludes that understanding and being responsive to the complexity of local realities, interests and contexts and the multi-layered practices of power may allow managers to adopt more appropriate management strategies.