Although BCG is attenuated, it is a live bacterium which repli-cates and survives in the host and is normally handled in BSL2 facilities. If a vaccine is to be successful in conferring protection against challenge with virulent M. bovis, it should induce immune responses capable of controlling/killing mycobacteria and it is rea-sonable to propose that this could initially be demonstrated by an ability to induce a reduction in the number of BCG cfu. Recently, a human BCG challenge model for the testing of TB vaccine can-didates has been described We proposed that such a BCG challenge model in cattle, once developed, could serve as a gat-ing criterion for this target species to screen vaccines before they are tested in expensive and facility-intense M. bovis challenge experiments. This paper describes the development of a cattle BCG challenge model.