Pigmented rabbits were sensitized by subcutaneous injection of BCG together with Freund's complete adjuvant and heat killed tubercle bacilli together with adjuvant. After the titer of serum antibody to BGG was elevated or tuberculin skin test became positive, choroiditis was induced in these eyes by an injection of BGG or PPD directly through the posterior sclera in the vicinity of the optic nerve. The eyes were enucleated at various intervals and the choroid was studied by light and electron microscopy. In the choroid challenged with BGG, infiltrates such as polymorphonuclear leukocytes and lymphocytes were seen, in early stages, invading in the posterior segment and peripheral area near the ciliary body. These cells decreased in number within a few days, and after one week a few plasma cells were detected in the posterior uvea. In the choroid challenged with PPD, infiltration of monocytes and lymphocytes was seen in early stages, reaching its peak in 48 hours. After 4 and 5 days lymphocytes decreased in number, but monocytes showed mitotic and phagocytotic activity, and accumulated near the sclera. After one week typical epithelioid cells were detected along the suprachoroidal space. These events were restricted within the choroid. The results obtained suggest, that in the focal immune reaction of the choroid, the cellular sequence of events and the range of tissue involved are different depending upon the kinds of antigen used. It may indicate humoral immunity on one side and cell-mediate immunity on the other.