Topical administration of 0.1% or 1% chloroethyldeoxyuridine eyedrops caused a significant reduction in the severity of experimental herpes simplex iritis and stromal keratitis in rabbits. The healing effect caused by chloroethyldeoxyuridine was comparable to that obtained with 0.1% and 0.5% bromovinylde-oxyuridine eyedrops. The drug levels achieved in the anterior chamber fluid following topical application of 1% eyedrops of [2-14C]CEDU, a radiolabelled analogue of chloroethyldeoxyuridine, were well above the minimum concentration (0.1 microgram/mL) required for inhibition of herpes simplex virus type 1 replication. The beneficial effects of chloroethyldeoxyuridine on stomal keratitis and iritis appear consistent with its efficient penetration through the cornea.