Widal test was done before and 15 days after the last dose of T.A.B. (33 Children) Diphtheria (13) Tetanus (16), Pertussis (7) and Measles (7) vaccinations. The tremendous rise of Widal agglutinin titers after T.A.B. vaccination could not foul up the results of the Widal test if we follow closely the suggested diagnostic Widal criterion combining a titer of 1/80 or more for "O" and 1/60 or more for one"H" agglutinin with the other "H" agglutinins at a lower titer.