A protein allergen extracted from a rough strain of B. melitensis was titrated in sheep sensitized by vaccination with the attenuated B. melitensis strain Rev. I. Single doses of allergen were given per animal by the intradermal or palpebral routes. Doses over a 100-fold range produced delayed hypersensitivity reactions of similar magnitude by both routes. The most suitable method for application in the field was a dose of 50 mug given by the palpebral route (0.5 ml subcutaneously in the upper eyelid) with readings taken 48 hours after inoculation. Sheep vaccinated with H 38 adjuvant vaccine for 6 to 9 months showed positive reaction to the allergic test, whereas non-vaccinated non-infected sheep showed no reactions. No increase in agglutinations titers following allergic test was observed in either Rev. I or H 38 vaccinated sheep.