The inhibition rate of L(-)pantothenate as an antagonist of D(+)pantothenate was discussed from the viewpoint of growth and lipid metabolism. The growth rate of mice given pantothenate-deficient diets containing L(-)pantothenate (300 mg per 100g diet) was markedly decreased, and such pantothenate-deficient symptoms as "spectacle eyes" appeared. However, it was recovered by the simultaneous addition of D(+)pantothenate. This result suggets that L(-)pantothenate is an antagonist of D(+)pantothenate. The same phenomenon was observed in a rat experiment. The growth of rats given L(-)pantothenate was extremely poor but recovered by the simultaneous addition of D(+)pantothenate. Its complete recovery was seen when the ratio of L(-)pantothenate to D(+)pantothenate reached 100:1. The same tendencies were observed in the liver levels of total lipid, total cholesterol and triglyceride, and also in the lipoperoxide values. This experiment suggests that the inhibition rate of L(-)pantothenate to D(+)pantothenate in animals is similar to that of DL-omega-methyl pantothenate.