The object of the work presented was to elucidate the maintenance of foot and mouth disease (FMD) in Africa, to assess its risks and to define guidelines for its control. Part II shows that in cattle the carrie r state is a natural sequel of infection but that the virus is maintained in domestic animals only for a limited period in the absence of reinfection. Transmission of infection from carriers is infrequent. Part III describes investigations in free-living buffalo and shows that they are maintenance hosts of foot and mouth disease Virus (FMDV) which appear to have achieved an equilibrium with the virus so that lt causes them little harm. A single herd may maintain several virus types simultaneously for prolonged periods with a low probability of spillover into other species. Part IV describes antibody surveys and experimental infections in African wildlife. FMD antibody was demonstrated in 18 cloven hoofed species from only a few of which virus has been isolated. Kutlu, impala , warthog and bush pig were shown to be susceptible to experimental and contact infection, and elephant to experimental but not contact infection. The carrier state was demonstrated only in kudu. In the general discussion the following points are made: 1) Although cattle may carry virus for up to 2 years, the risk of their transmitting the infection is low. 2) Where FMD is endemic, successful routine prophylactic vaccination eliminates both disease and virus from domestic stock and also apparently from associated susceptible wild species other than buffalo. 3) Buffalo maintain FMDV independently of cattle but, in the absence of visible lesions, normally shed insufficient virus to infect other species. 4) Infected cattle however shed sufficient virus to infect susceptible wild animals (e.g. impala, kudu) which in turn may infect other cattle. 5) This cycle of infection can be broken by vaccination of domestic stock, protecting both the livestock and wild life industries.