Using recently published information, we examined the experience of a hypothetical cohort of 1 million children followed up from birth to 6 years of age without and with a pertussis vaccination program. Costs associated with death or lost wages were not estimated. A vaccination program reaching 90% of children would reduce disease incidence and disease-related costs by 90%. Taking into account costs associated with vaccine and vaccine reactions, the costs are reduced 82%. The ratio of overall costs without a program to those with a program is 5.7:1. The benefit-cost ratio is 11.1:1. Because we did not include indirect costs, this is a conservative estimate. Until improved vaccines are available, continued use of our present vaccines, with careful attention to possible contraindications, seems the only prudent course to follow.