SummaryAdditional data on the tuberculin hemagglutination test in various types of tuberculous infection have been presented. The reproducibility of the test has been examined by running duplicates at different times. BCG vaccination in the neo‐natal period evokes a agglutinin response only after a relatively long period of time, whether or not the child has additional exposure to tuberculosis. Infants having such exposure develop higher titers, without having clinical evidence of any superinfection. Re vaccination with BCG evokes an anamnestic type of antibody response. The anamnestic response is not activated sufficiently or promptly enough by tuberculin testing to affect hemagglutinin studies within 2 weeks after the first tuberculin test. –