SUMNMARYAlthough we have failed to produce either paroxysmal cough or vomiting in rhesus monkeys, cynomolgus monkeys and marmosets, we have found in marmosets several features of pertussis infection similar to those seen in children with whooping cough: catarrh, persistence of colonization of the naso-pharynx with Bordetella pertussis for 4-11 weeks, change of serotype during colonization and inability of type 1 organisms to establish themselves as the predominant serotype.As in children, we have found that intramuscular vaccine of type 1,2,3 was more effective than type 1,2 in preventing persistent infection with the currently prevalent serotypes 1,2,3 and 1,3. A mixed vaccine (1,2,3 and 1,3) seemed to produce agglutinin 3 in the serum more consistently than a pure type 1,2,3 vaccine. The duration of colonization, after naso-pharyngeal challenge, was greatly reduced in animals with agglutinin 3.Local immunity, resulting from previous infection, was even more effective than a good vaccine in preventing subsequent persistent colonization. Marmosets may be useful in studying the possible development of aerosol pertussis vaccine for human use.