Summary 1. Limestone and sodium bicarbonate were compared as neutralizers when fed with oat silage preserved with 20 pounds of 68 per cent phosphoric acid per ton of green material. Sodium bicarbonate proved to be considerably more efficacious than limestone. 2. Sodium bicarbonate was about twice as efficient as limestone; in counteracting the acid in phosphoric acid oat silage. On the two-hydrogens-neutralized basis, limestone was not completely effective in either curative or preventive trials, whereas the quantity of sodium bicarbonate sufficient to neutralize one hydrogen of the acid in the phosphoric acid oat silage proved to be slightly superior. Sodium bicarbonate and limestone when fed in equivalent amounts to neutralize two hydrogens of the phosphoric acid were adequate, and this combination is probably the most satisfactory for practical purposes. Sodium bicarbonate when fed on the two-hydrogens-neutralized basis proved to be efficient. 3. There is apparently a relation between the acid condition of the animals and the amount of silage consumed, because after adequate neutralization of the acid the silage consumption increased rapidly. 4. A grain mixture containing two per cent limestone along with a mixed alfalfa-timothy hay of good quality proved to be ineffective in preventing acidosis in cows fed phosphoric acid oat silage in a long-time feeding experiment.