The Community Action in Public Health Study explored how public health managers, frontline staff, and community participants interpret, implement and receive policy guidelines urging collaboration with community groups in public health work. In-depth case studies of 6 public health units in Ontario, Canada focussed on 19 community development projects in 3 program areas (107 interviews). In the absence of formal policy guidelines on community development at provincial or local levels, informal policy predominated. Local senior management frequently set the tone, distinguishing health units in which community development was a basic philosophy underlying a broad spectrum of public health practice from those in which it was seen as only one among many possible strategies. Uncertainty and risk associated with informal policy lead many frontline staff to adopt strategies intended to preserve autonomy in community work, including "seeking forgiveness rather than permission" and maintaining relative "invisibility."