Proteases are involved in the pathogenesis of Pseudomonas aeruginosa infections of the cornea. Although there are many potential roles for these enzymes, involvement in corneal stroma destruction with subsequent descemetocele formation and/or corneal perforation is an important example. This study examined the relationship of elastase and alkaline protease to corneal destruction as indicated by descemetocele formation. The protease content of the overnight Mueller-Hinton broth cultures of various strains ofP. aeruginosa correlated with the production of descemetoceles both in the rabbit trauma model of Pseudomonas keratitis and upon intrastromal injection of filtrates of the overnight culture media. The levels of alkaline protease correlated better with descemetocele formation than those of elastase. The influx of inflammatory cells was not correlated with descemetocele formation within 24 to 48 hrs.