Nine infants, 1 to 12 months of age, with convulsions due to inapparent cause, have remained free of seizures after a change to a diet providing an increased amount of vitamin B6, or after administration of vitamin B6 as such. Five of these infants had been receiving a proprietary milk mixture found by analysis to be low in content of vitamin B6 (0.085 mg/l), two were breastfed and two, who developed convulsions in the neonatal period, had been receiving an evaporated milk mixture. Seven of the infants became free of convulsions when given an evaporated milk mixture supplying an average of 0.26 mg of vitamin B6 daily. Four of these seven infants were studied for biochemical evidence of deficiency of vitamin B6 by the use of a tryptophan loading test. All four excreted large amounts of xanthurenic acid after receiving 0.54 gm/kg of DL-tryptophan. One to 1.4 mg of vitamin B6 daily were required to prevent the excretion of xanthurenic acid. In contrast, 10 of 11 control infants receiving 0.2 to 0.5 mg of vitamin B6 daily failed to excrete xanthurenic acid when similarly tested and two of these infants, who began to excrete xanthurenic acid after receiving for 1 month a diet low in content of vitamin B6, ceased to do so after receiving 0.3 to 0.4 mg of vitamin B6 daily. This suggests that the requirement of vitamin B6 of the seven infants who had developed the deficiency is, for some reason greater than that of the average infant. The two infants whose convulsions appeared in the neonatal period required 2 to 5 mg of vitamin B6 daily to eliminate the seizures. One of these is still dependent upon a supplement of 2 mg of vitamin B6 daily. However, these two infants, like the control infants, required only 0.3 to 0.4 mg of vitamin B6 daily to prevent excretion of xanthurenic acid after receiving a dose of tryptophan. It seems probable that these two infants have anomalous metabolism of vitamin B6 rather than simple deficiency. In view of the above observations, it is recommended that an infant's diet contain 0.2 to 0.3 mg of vitamin B6 daily. However, since there are occasional instances of anomalous requirements, it is suggested that a therapeutic trial dose of 5 to 10 mg of pyridoxine hydrochloride daily be given to any infant with convulsions resulting from inapparent cause.