Keratitis caused by Pseudomonas aeruginosa usually occurs in the setting of corneal injury. This investigation was carried out to ascertain whether injury predisposes to infection by permitting this organism to adhere to the cornea. P. aeruginosa was found to adhere to injured corneas in preference to uninjured ones. Adherence was not immediate and required that the organisms remain on the corneal surface for some time. The number of adhering bacteria appeared to increase with the time the bacteria were allowed to remain on the corneal surface. Use of inocula concentrations of 10 (7) to 10 (9) was best for studying this phenomenon quantitatively and by microscopy. We conclude that injury allows Ps. aeruginosa to adhere to the corneal surface and suggest that this is the explanation for the clinical observation of a relationship between corneal and injury and Pseudomonas keratitis.