OBJECTIVE: To calculate the cost-effectiveness, expressed in dollars per quality-adjusted life years (QALY), of increasing measles immunization rates. DATA SOURCES/STUDY DESIGN: Published data were supplemented by expert opinion. We determined the cost savings and value of the health benefits from averting a single case of measles. Next we examined the U. S. data regarding the relationship between pre-school measles immunization and incidence rates. Finally, we calculated the cost-effectiveness of a program that would increase a locality's immunization rate to the point of disease elimination. PRINCIPAL FINDINGS: Averting a single case of measles, using "base case" assumptions, yields societal cost savings of $2,089 and an increase of 0.086 QALYs. Using a very low discount rate increases the total benefits to $2,251 in societal cost savings and 0.150 QALYs in health benefits. In general, programs to raise measles immunization rates are not cost-effective, except possibly during an outbreak of the disease or in areas with very low immunization rates. The extremely low measles incidence rates in the mid-1990s result in such programs having extremely high costs per QALY gained. CONCLUSIONS: Programs that are narrowly designed to increase immunization rates alone are not likely to be cost-effective. Yet these programs do have the potential to be cost-effective if the program design and evaluation also recognize the benefits associated with the primary and preventive care that can accompany immunizations. Such programs may also be cost-effective if they are components of a global eradication of measles.