Eighty-five Cameroonian infants aged between 3 and 8 months were vaccinated with a high-dose Edmonston-Zagreb (EZ) strain (10(5.6) TDIC50), 81 with a low-dose Connaught strain (10(3) TCID50) and 74 with a medium-dose Schwarz strain (10(4) TCID50). Side-effects were mild (less than 32% of infants) and were not significantly different among the groups, nor were postvaccination anti-measles antibody levels. Postvaccination seropositivity and seroconversion rates were respectively 91.6% and 69% for EZ, 85.3% and 67.7% for Connaught and 75.6% and 62.2% for Schwarz. In the light of concerns regarding high-titre measles vaccines, the overall performance of the Connaught strain warrants its wider evaluation in young infants.