Vitamin A-deficient rabbits were used to evaluate the role of secondary bacterial infection in the development of keratomalacia and to describe the resultant clinical and morphologic alterations. The conjunctival sacs of vitamin A-deficient rabbits at different stages of corneal involvement were inoculated with Pseudomonas aeruginosa topically. Approximately two weeks after inoculation, corneal ulceration with stromal melting developed in one of three eyes with severe punctate keratitis and in four of seven eyes with xerosis. Ulceration did not develop in any of the eight eyes with early epithelial graying or mild punctate keratitis. Inflammatory cells (primarily polymorphonuclear leukocytes) infiltrated the anterior corneal stroma of infected corneas. Liquefaction of collagen was observed in association with bacteria alone, as well as in association with polymorphonuclear leukocytes. No signs of infection were observed after conjunctival inoculation of Pseudomonas in the eyes of nine control rabbits.