Between 1994 and 1996, the United States Agency for International Development (USAID) closed 23 country missions worldwide, of which eight were in West and Central Africa. To preserve United States support for family planning and reproductive health in four countries in that region, USAID created a subregional program through a consortium of US-based groups that hired mainly African managers and African organizations. This study assesses cost-effectiveness of the program through an interrupted time-series design spanning the 1990s and compares cost-effectiveness in four similar countries in which mission-based programs continued. Key indicators include costs, contraceptive prevalence rates, and imputed "women-years of protection." The study found that, taking into account all external financing for population and family planning, the USAID West Africa regional approach generated women-years of protection at one-third the cost of the mission-based programs. This regional approach delivered family planning assistance in West Africa cost-effectively, and the findings suggest that regional models may work well for many health and population services in small countries.