Among the problems encountered today in Expanded Programs on Immunization (EPI) is the failure to reach an acceptable level of immunization coverage in rapidly growing urban areas. This paper describes a checklist for identifying the reasons for such low coverage. The checklist was first used in Yaounde, United Republic of Cameroon. There the low coverage is associated with certain neighborhoods, 1 ethnic group, low socioeconomic status, and newly-arrived families. Publicity about immunizations is not reaching Yaounde residents in those categories. Health lessons (given only in French) seem to be confusing the parents rather than educating them. Previous ineffective immunization programs have made Yaounde residents mistrustful of the current program. Solutions for each of these Yaounde problems are recommended. The checklist, and the methods used for answering it in Yaounde, should prove useful for other immunization programs.