Abstract The serious economic consequences of Dermatophilus congolensis infection on animal production have been known for many years but the epidemiology and pathogenesis of the disease are still poorly understood and effective methods for its control remain to be developed. The factors underlying the severity of dermatophilosis in certain regions are particularly obscure. Experimentally it has not been possible to reproduce the severe generalised disease as seen in the field and there is no doubt that other factors which diminish skin resistance or potentiate the level of infective challenge are involved in its pathogenesis. These include the activities of biting arthropods and intercurrent disease. In some areas where it has been possible to control such factors dermatophilosis has been substantially reduced in incidence and severity but this is not practicable in extensive types of husbandry. A means of combating dermatophilosis more directly is thus required. It is recognised that a degree of natural immunity to dermatophilosis exists, particularly in certain breeds of cattle, and that resistance in individuals is genetically determined. Studies of mammalian skin structure and the response to experimental inoculation indicate that this immunity is related, in part, to the protective effect of the keratinised cells and secretions present at the skin surface and to the cellular immune response to infection. Although ‘normal’ antibodies to Dermatophilus are found in animal sera and antibody production is stimulated by natural infection, they do not confer immunity. Delayed hypersensitivity which develops following infection and may be associated with accelerated healing of lesions in some species is also not protective. Nevertheless some workers have described the existence of immunity to reinfection following experimental inoculation and it is apparent that resistance can be considerably enhanced under experimental conditions by the use of certain types of live vaccine. As yet it has not been possible to consistently obtain equivalent results in field trials. Recent studies show that a specific secretory immune response is provoked at the skin surface by administration of a live intradermal D. congolensis vaccine and raise the possibility of humoral defence at the level of the epidermal stratum corneum. It is clear that much work remains to be done in defining the nature of the antigenic stimulus required to provoke a protective response suitable for field use and to elucidate the immune mechanisms underlying such a response.