Of 7 individuals given routine army vaccination for cholera, 6 developed Brucella agglutinin titers in dilutions ranging from 1:50 to 1:500. Of 27 persons given varying amts. of an exptl. cholera vaccine (extracted cell residue containing only O antigen), 2 developed Brucella agglutinins in titers of 1:25 and 1:50, the rest remaining negative. All of those vaccinated developed high titers for Vibrio comma. Reciprocal agglutinin absorption tests indicate that an H antigen of V. comma is also present in Brucella.