In the field of HIV/AIDS, social movement organisations (SMOs) have been identified as powerful potential catalysts for change through their impact on formal organisational structures and the policy process. In addition, they have the capacity to be important providers of services in their own right, through the community resources they are capable of mobilising. In the United Kingdom, however, their role in policy formation is disputed. Previous studies have concluded that they have been most influential at national policy and ward level. At the level of local policy making, their influence has been found to be patchy and confined largely to securing recognition of HIV as an issue. Most previous research has, however, been conducted in high prevalence, metropolitan settings with functional SMOs. This paper presents the results of a comparative case study of two neighbouring provincial low prevalence district health authorities (HAs) in England. We describe the changing national policy context from 1986 to 1995 and use a strategic change model to analyse the local development of care and treatment services for people with HIV/AIDS, in particular the relationship between SMOs and HAs. Despite being demographically, socioeconomically and epidemiologically similar, and sharing an identical national policy framework, the two districts demonstrate completely divergent organisational responses to the HIV/AIDS epidemic. We conclude that the level of prior social movement mobilisation and the degree of receptivity for change within the HA are the key variables for explaining variations in the scale of strategic change observed in the two districts.