Three groups of 10 foxes were vaccinated by the direct oral instillation of 2 ml of SAG1 rabies virus vaccine containing 10(6) MICLD50 (10(7) TCID50/ml) infectious viral particles/ml. SAG1 is a natural variant of the attenuated rabies vaccine strain SAD Bern and was selected in the presence of monoclonal antibodies. The strain is devoid of residual pathogenicity for the fox and the highly susceptible adult laboratory mouse by the oral, intramuscular and intracerebral routes. The foxes were challenged six, 12 and 18 months later with a virulent vulpine street rabies virus (GS 7-1-1). They all survived, whereas seven of eight unvaccinated control foxes died.