BACKGROUND:  Measles vaccine (MV) has a greater effect on child survival when administered in early infancy, when maternal antibody may still be present. To test whether MV has a greater effect on overall survival if given in the presence of maternal measles antibody, we reanalysed data from two previously published randomised trials of a two-dose schedule with MV given at 4-6 months and at 9 months of age.<br/> METHODS AND RESULTS:  In trial I (1993-95), the mortality rate was 0.0 per 1000 person-years among children vaccinated with MV in the presence of maternal antibody and 32.3 per 1000 person-years without maternal antibody; mortality rate ratio (MRR)=0.0 (95% CI 0-0.52). In trial II (2003-07), the mortality rate was 4.2 per 1000 person-years among children vaccinated in presence of maternal measles antibody and 14.5 per 1000 person-years without measles antibody; MRR=0.29 (0.09-0.91). Possible confounding factors did not explain the difference. In a combined analysis, children who had measles antibody detected when they received their first dose of MV at 4-6 months of age had lower mortality than children with no maternal antibody, the MRR being 0.22 (0.07-0.64) between 4-6 months and 5 years.<br/> CONCLUSIONS:  Child mortality in low-income countries may be reduced by vaccinating against measles in the presence of maternal antibody, using a two-dose schedule with the first dose at 4-6 months (earlier than currently recommended) and a booster dose at 9-12 months of age.<br/>