Corneal opacity and vascularization occurs following repeated or chronic chlamydial ocular infections and may results in blindness. The mechanisms resulting in corneal opacity are known but may be caused by hypersensitivity to chlamydial components. To study corneal involvement during chronic chlamydial infections, we have developed an animal model using guinea pigs treated topically with penicillin during infection with C. psittaci strain GPIC. Corneal opacity and vascularization occurs only in animals simultaneously infected with GPIC agent and treated with penicillin. Opacity resolves with clearance of GPIC agent from the conjunctivae; however, the cornea sustains permanent damage as evidenced by vascularization and scarring observed months after resolution of opacity. This animal model will be useful to study the role of chlamydiae and chlamydial components in the development of corneal damage during chlamydial infections. C. psittaci strain GPIC can infect the genital tract in addition to the conjunctiva. We have utilized this model to determine if hypersensitivity to chlamydiae occurs in the oviduct and uterus of guinea pigs recovered from a previous vaginal infection. The uteri and oviducts of these animals develop significant inflammation following inoculation of an extract of C. psittaci strain GPIC. This inflammation needs to be further characterized to determine whether it is characteristic of delayed hypersensitivity or of cellular toxicity.