Cultures of Bordetella pertussis were isolated by pernasal swabs from Kenyan children in whom whooping-cough was suspected. Serotyping of 94 of these isolates was undertaken by four laboratories in Europe, and there was very close agreement in their typing results. Each laboratory found that the incidence of type 1, 3 was the lowest of the three types, and that there were approximately equal numbers of types 1, 2, 3 and 1, 2. No new serotype was found. This distribution of serotypes was found in all age-groups; and it is in marked contrast with that currently seen in vaccinated communities, where type 1, 3 predominates. The implications of these findings for vaccination against whooping-cough in East Africa are discussed.