With young mice fed on B(6) deficient synthetic food for 30 days the author observed general conditions of these animals and also carried out biochemical studies on their cerebral cortex. Some of them were subjected to intravenous injection of desoxypyridoxine, known to possess competitive action against B(6), and changes in their cerebrum were investigated. The follwing are the results of the present study. 1. In the mice fed on B(6) deficient food the gain in the body weight is inhibited when compared with the control group kept on normal diet. More than one month later these B(6) deficient animals show the falling off of hairs and reddening around their mouth and the coarsening of body hairs. 2. In the mice fed on B(6) deficient food a definite decrease in cholinesterase activity (ChE) can be observed in their cerebral cortex when compared with the control group. In those with experimental epilepsy elicited by the intravenous injection of desoxypyridoxine, a marked diminution of ChE can be recognized. 3. While there can be seen no significant difference in the contents of Na and K in the cerebral cortex of the mice fed on B(6) deficient food when compared with those of the control an increase of Na and a decrease of K can be recognized in those animals with epilepsy induced by the intravenous injection of desoxypyirdoxine. 4. In the micc fed on B(6) deficient food there can also observed an increase in free water of the cerebral cortex.