The local immunity of the ocular surface is governed by conjunctival-associated lymphoid tissue (CALT), secretory IgA and immunocytes. The authors performed a histological investigation of the time-course changes in CALT caused by invasion of antigen to the ocular surface through the instillation of horseradish peroxidase (HRP) into the guinea pig eye. We used PAS staining, peroxidase staining, alkaline phosphatase staining. The lymphoepithelial cells of CALT phagocytized HRP 30-60 min after the instillation, and formed intraepithelial pockets 24 hours after instillation. The follicular area of CALT was strongly positive for alkaline phosphatase 2 weeks after instillation. These changes were considered to be the first step in the manifestation of local immunity on the ocular surface. Each staining technique revealed differences between the lymphoepithelium and conjunctival epithelium, suggesting that lymphoepithelium has characteristics different from those of conjunctival epithelium.