In 2002 we estimated the measles cumulative vaccination coverage (CVC) in Japan by randomly selecting a total of 5,000 3-year-old children from the total Japanese population and examining the age in months when they were vaccinated against measles. This survey revealed that in Japan measles CVC at ages 18, 24, and 36 months were 61.7 +/- 1.6%, 79.6 +/- 1.3%, and 86.9 +/- 1.1%, respectively. The results obtained in 2003 revealed that the measles CVC among 3-year-old children in 2003 was higher than that obtained in 2002, with especially noticeable improvement in their period of 12 to 23 months of age. It is estimated that this improvement was attributed to the effort made by many persons concerning vaccination to raise the vaccination rate. In 2003 oral polio vaccine (OPV) CVC was investigated for the first time, in addition to measles CVC. OPV CVC of the first dose at 6, 12, and 36 months of age were 44.2 +/- 1.5%, 85.5 +/- 1.1%, and 94.7 +/- 0.8%, respectively. The results of the second dose at 12, 18, and 36 months of age were 42.3 +/- 1.5%, 73.5 +/- 1.3%, and 90.7 +/- 0.9%, respectively. Even at 36 months of age the CVC level of the second dose of OPV was found to be slightly lower than that of the first dose.