Years ago, Fisher and Allen (7) suggested that the characteristic damage observed with P. aeruginosa eye infections may be attributable to the action of bacterial proteases on the corneal proteoglycan. Several groups, including Kawaharajo et al. (16), Hirao and Homma (12), Kreger and Gray (20) and Kreger and Griffin (21) have since provided data to support this hypothesis. Recently, Ohman et al. (27) initiated a genetic study to examine the role of bacterial toxin and protease in corneal infection. They examined the virulence of an elastolysis-deficient mutant of P. aeruginosa and concluded that elastolysis was not required to establish an active infection. They also concluded that if extracellular protease is required for virulence in Pseudomonas eye infections, then alkaline protease produced by the mutant strain they examined may have been sufficient to cause corneal damage.