Effects of different vitamins on concentration of blood serum components and amino acid were studied, using male rats of the Wister strain. Five kinds of vitamins, namely vitamin A, v. B1 (thiamin), v. C (ascorbic acid), v. D (calciferol), v. E (tocopherol) were used in this study. They were injected sub cutaneously in a single dose of 500 IU, 2.5 mg, 2.5 mg, 1000 IU and 2.5 mg, respectively. The animals were sacrificed by decapitating at four hours following the injection. Blood sample taken at the time of sacrifice was centrifuged for separation of serum after 10 hours-standing at room temperature. The serum was determined for concentration of its components, using Vet-Aid described previously and analyzed for amino acids, using a full automatic amino acid analyzer previously described. Concentration of cholesterol in the serum was elevated by the administration of vitamins A, B and C, and it was lowered significantly by the administration of vitamins D and E. These vitamins seemed to have a close relation to fat deposition in the meat. The effect of vitamins on fat deposition in beef would require further study