A commercial live feline-chlamydial vaccine and four experimental inactivated preparations were compared on the basis of clinical protection in cats challenged conjunctivally and intranasally with Chlamydia psittaci. Best protection was afforded by the live vaccine. Good results were also obtained using inactivated preparations of a recent feline conjunctival isolate. Protection did not correlate with the development of complement fixing antibodies but may be related to the induction of a cell mediated response as assessed by the lymphocyte blastogenesis test.