The study was undertaken to compare the antibody response of 6-12 weeks old infants after three doses of standard trivalent oral polio vaccine (TOPV) (Groups A; (n = 42) with three doses of double the amount of TOPV (Group B; n = 35). Seroconversions in Group A were 64.2, 80.9% and 57.1% for Types I, II and III polioviruses, respectively. The corresponding figures for Group B were 77.7, 80.0 and 60.6%, respectively, the differences being insignificant. Differences in feeding practices and presence of maternal antibodies did not affect seroconversion. This suggests that increasing the amount of vaccine virus in each dose is not an alternative to present strategy. Breast feeding and presence of maternal antibodies are not responsible for poor seroconversion.