It was shown in the passive hemagglutination test (PHAT) with a type-specific 
somatic antigen on 147 carriers of toxigenic diphtheria bacilli that the PHAT 
titres of 1/80 and over were determined in 64% of bacteria. In the process of 
carrier state of toxigenic bacteria antimicrobial antibodies were detected in 
79% of the children; after the release from the carrier state, the percentage 
was from 57 to 26, depending on the time lapse after it. Among the carriers of 
nontoxigenic diphtheria bacilli the PHAT titre of 1/80 and over was established 
in up to 20% of children, and only in those which were in the focus of toxigenic 
bacilli carriers. The applied test could be used for epidemiological purpose to 
determine the spread of the carrier state of toxigenic bacteria in a collective 
body.