Different levels of monosodium glutamate (MSG) in conjunction with vitamin levels have been studied in successive generations of mouse. At each vitamin level, 1 and 2%, the mice received diets which contained MSG 1%, 2%, no MSG (control group). Litters of the 1st and 2nd generation were studied for RNA, DNA, protein content, and the cellularity in the brain. The diets with MSG addition increase the percentage of rearing, and the average weight of the treated animals at weaning is higher than in controls. The data on the cellularity of the central nervous system show no significant difference between animals treated with high daily doses of MSG and control animals. This confirms that prolonged oral administration of MSG in successive generations does not have a negative effect on the development.