Phospholipase A 2 s (PLA 2 s) are a family of esterases that initiate the arachidonic acid cascade, which results in the production of numerous inflammatory mediators. We investigated the expression of Group I and II PLA 2 proteins and Group II mRNA in normal conjunctivae and in the conjunctivae of mice with compound 48/80-induced conjunctivitis. Conjunctivitis was induced in C57BL/6 mice by topical instillation of compound 48/80 (C48/80). Mice were then treated with corticosteroid (Pred Forte), antiflammin-2 (AF2, a synthetic peptide that inhibits PLA 2 ), or a placebo (Dacriose, an isotonic, buffered, sterile eye irrigating solution). Low levels of PLA 2 s were detected on the epithelium of normal conjunctivae. One hr after C48/80 instillation, the expression of PLA 2 s appeared and increased in the substantia propria, peaked at 6 hr, and returned to baseline 72 hr later. Compared to the placebo, the conjunctivitis was moderate in the AF2-treated group and mild in Pred Forte-treated group. The expression of PLA 2 s was suppressed in mice treated with Pred Forte and AF2. iNOS mRNA was also diminished in the AF2- and Pred Forte-treated groups. The mechanisms by which anti-allergic medications suppress conjunctivitis may involve the inhibition of PLA 2 s and iNOS.