To evaluate the etiology of corneal opacities, a study was done on the immunohistochemical staining for heat shock protein (HSP) 72/73 and c-fos after myopic excimer laser photorefractive keratectomy (PRK). New Zealand white rabbits (60 eyes) were divided into four groups: -6-, -9- and -15-dpt operation groups and a control group (only corneal epithelium removed). Using an excimer laser (VisX 20/20, Sunnyvale, Calif., USA), myopic PRK was performed on the rabbit's cornea by a single or multizone technique followed by an immunohistochemical stain to detect the expression of HSP 72/73 and c-fos at 6, 24, 48 h, 1 week and 8 weeks. Corneal epithelia were healed within 3 days in all groups, and 8 weeks after the operation, the mean density of corneal opacity was 0.83 (-6-dpt operation group), 1 (-9-dpt operation group) and 1.67 (-15-dpt operation group). All groups exhibited HSP 73 in corneal epithelium and stroma. However, the maximal expression of c-fos and HSP 72 appeared in corneal epithelium at 24 and 48 h, respectively, after the operation in the -15-dpt group. These results suggest that the expressions of HSP 72 and c-fos in rabbit corneal epithelium are significant factors in relation to corneal opacity after excimer laser PRK.