The Expanded Program on Immunization has made remarkable progress in raising coverage in developing countries. Countries have been urged to accelerate their programs, especially in urban areas. In Mozambique, as part of program acceleration, volunteers from grassroots organizations conducted door-to-door canvassing for the Program. Concurrently, the availability of immunization was increased in health centers and in outreach visits. By 1987, over 90 percent coverage for all vaccines was achieved in the capital, Maputo; two other cities doubled their immunization coverage to over 50 percent fully immunized children, and rural areas of the pilot province achieved 60 percent coverage. Immunization costs were estimated in one city as $6.9 (U.S. dollars) per fully vaccinated child. Door-to-door canvassing accounted for more than 40 percent of personnel costs, and may have diverted attention from the quality of service in the health centers. In this article we outline the achievements and costs of door-to-door canvassing and discuss other strategies to raise coverage. The analysis of the need to balance the mobilization of demand with the capacity to respond is relevant to other countries in their efforts to develop sustainable immunization services.