This paper extends a cross-country analysis of health determinants with a civil society variable. The reason is that next to government and households and the level of economic development, civil society agency is likely to play a role in health care as well. This role refers to community care, political pressure, and demands for accountability of health care providers. We use the ISD index of civic activism to measure the agency of civil society. The panel regression results for developing counties indicate that civic activism contributes to the reduction of child mortality and maternal mortality. The size effect is larger than that of almost all other variables, except those for health expenditures. This implies that in times of severe financial constraints, civic activism may be the relatively most feasible factor stimulating better health outcomes.