The effects of oral administration of the extracts from the leaves of several Artemisia species, and of chlorogenic acid, which is one of their components, and also of caffeic acid (which can be produced by partial hydrolysis of caffeoylquinic acids, which are the main polyphenolic components in these species) on lipid metabolic injury produced in rats by feeding peroxidized oil were investigated. The acetone-water extracts of the leaves of Artemisia princeps, A. montana and A. capillaris reduced the elevation of lipid peroxide concentration in the serum in peroxidized oil-fed rats, and the above extracts reduced the levels of liver triglyceride. The extracts of A. montana and A. capillaris inhibited the elevation of serum glutamic oxaloacetic transaminase and glutamic pyruvic transaminase. Caffeic acid and chlorogenic acid also inhibited the elevation of serum triglyceride, lipid peroxides, total cholesterol, glutamic oxaloacetic transaminase and glutamic pyruvic transaminase, as well as liver lipid peroxide.