Excised cornea from adult New Zealand rabbits were incubated with progesterone-4-14C in Eagle's media for 96 hr. Samples were inactivated at intervals of 24 hr incubation periods. The following metabolites of progesterone were isolated: 20 alpha-Hydroxy-4-pregnen-3-one, 20-hydroxy-4-pregnen-3-one, 5 alpha-pregnane-3,20-dione; 5 beta-pregnane-3,20-dione and 6 beta-hydroxy-4-pregnen-3,20-dione. 20 alpha-Hydroxy-pregnen-3-one was the predominant metabolite of progesterone-4-14C. A linear increase was observed throughout 96 hr. The opposite was found for 5 alpha and 5 beta pregnane-3,20-dione. Compounds remaining at the origin of the paper chromatograms contained 6 beta-hydroxy-4-pregnen-3,20-dione and other still unidentified metabolites of progesterone-4-14C. Presence of 20 alpha and 20 beta-reductase; 5 alpha and 5 beta-reductase and 6 beta-hydroxylase enzyme systems are involved in corneal progesterone metabolism. No fungal neither bacterial enzymatic biotransformation occurred in the culture media.