118 infants under 3 years of age were thrice orally immunised against poliomyelitis at 2 months interval. Before the vaccination 26% were triple negative and 24% triple positive. 44% had neutralising polio antibodies type 1, 53% type 2 and 52% type 3. At the end of the vaccinations 59% of the vaccinees were triple positive and only 3.4% triple negative. 82% had polio antibodies type 1, 85% antibodies type 2 and 76% antibodies type 3. At the start of the trial 54% of the vaccinees excreted enteroviruses. Only in 12% young infants had enterovirus in anal swabs and seroconverted well. In view of the prevalence of paralytic poliomyelitis in tiny babies an early oral polio immunisation in the tropics is highly recommended.