A serological survey to determine susceptibility rates to rubella and measles was conducted among first graders in Cincinnati during 1972. Sixty-three percent (858) of the eligible first graders participated. The overall susceptibility rates to rubella and measles were 21% and 7%, respectively. The susceptibility rate to rubella was down from 75% found among first graders in an adjacent school district in 1968. However, the lower socioeconomic group of first graders had a significantly higher susceptibility rate. The middle socioeconomic group had a significantly higher susceptibility rate to measles. The failure rates for rubella and measles vaccines were 13% and 7%, respectively, indicating a need for follow-up serologic studies to determine persistence of vaccine-induced antibodies.