Weanling female Sprague Dawley rats were fed diets containing 22mg pyridoxine HCI/kg diet(control diet) and 1.2mg pyridoxine HCI/kg diet(deficient diet). One deficient group and one control group were fed their diets throughout the period of growth, gestation and lactation. After the pups were born and weaned, the deficient group was divided into two groups. Therefore, one(DC) switched to control diet and the other continued the same deficient diet until 10 week-old. Analysis of chemical composition of fatty acid in the total brain lipid was conducted in the pups of 5, 10, 15, 21, 35, 50 days of age. Arachidonic acid content was significantly decreased in the deficient group at 5 days compared to the control, but at almost all ages, there were no significant differences in fatty acid contens among all the groups. The fatty acid compositions of the brain phospholipids were determined on pups at 1, 14, 21, 35, 70 days of age. The content of $C_{20}\;_{4}$ in the brain phosphatidylcholine birth and contents of $C_{22}\;_{4}$ and $C_{22}\;_{5}$ at birtd, and $C_{22}\;_{5}$ and $C_{22}\;_{6}$ at 14 days in the phosphatidylethanolamine were depressed in the deficient group. These changes were not consistent with ages. Therefore, it may reflect that the major part of the changes occuring in the pyridoxine depleted rats depends, not so much on the pyridoxine depletion itself, as on the age or development of the rats.