Myeloperoxidase (MPO) activity was measured in rabbit cornea and iris-ciliary body to quantitate the infiltration and accumulation of polymorphonuclear leucocytes (PMN's) following an inflammatory stimulus.Following injection of clove oil into the cornea, MPO activity could be detected in the cornea at 6 hr, reaching a maximum at 12 hr, and falling to non-detectable levels at 72 hr., MPO activity was only detected in the iris-ciliary body 24 hr after intracorneal clove oil injection.MPO activity in the iris-ciliary body increased in a dose-dependent manner following intravitreal injection of endotoxin. No MPO activity could be detected in cornea.Topical administration of dexamethasone inhibited MPO activity in cornea and irisciliary body 24 hr after intracorneal clove oil and intravitreal endotoxin injection, respectively.Measurement of MPO activity in ocular tissues could provide a useful tool to quantitatively evaluate the severity and time course of inflammation.