Measles vaccination of infants younger than 1 year of age should be successful in populations with a high proportion of measles vaccinated mothers. Infants whose mothers were vaccinated are born with less maternal antibody which can interfere with vaccination compared with infants whose mothers had measles. AIK-C or Connaught (CLL) measles vaccine was given to 300 6 month infants born to mothers who had measles (group 1) or who were vaccinated against measles (group 2). Pre- and post-vaccination measles antibody was measured by EIA and PRN and cell mediated immunity (CMI) by blast transformation and production of interferon-gamma and interleukin-10. After vaccination, mean antibody level, seroconversion and blastogenesis were significantly lower for group 1 than group 2 (p < 0.05). Post-vaccination measles IgG was significantly higher for group 2 CLL vaccinees compared with group 2 AIK-C (p < 0.05); seroconversion rates were 73 and 63%, respectively. More than 93% of group 2 infants had elevated measles IgG after vaccination. About 89% of all children had some evidence of a blastogenic response. Lymphoproliferation correlated strongly with cytokine production and weakly with IgG. Not all seroresponders had a CMI response and vice versa. AIK-C and CLL vaccines induce strong measles specific T and B immunity in most 6 month infants of vaccinated mothers.