1. Intramuscular injection of chrome vaccine in horses was favourable from the viewpoint of clinical reactions and antibody production. 2. Heat-killed vaccine injected subcutaneously caused early local and systemic reaction and its rapid disappearance compared with chrome vaccine. 3. Chrome vaccine and oil chrome vaccine showed high tendency to cause suppuration when they were injected intra- or subcutaneously. 4. Foals generally react more slightly than two-year-old colts. 5. Marked increase of antigenicity was not observed in chrome vaccine. 6. Peanut oil adjuvants without lanoline had no enhancing effect on chrome vaccine. 7. Duration of antibody production in 5〜8.5 months old foals is shorter than that in two-year-old colts
