Bloat can be produced at will if lactating cows are deprived of hay and bedding for at least 48 hours and pastured on thick stands of immature alfalfa free of weeds and grasses. The animals must be accustomed to the field as they may not eat consistently the first 2 or 3 days. In one instance 10 of 17 cows bloated after 2¾ hours on pasture. Of 17 lactating cows used 14, bloated at least once during the experiments. Some, however, were more subject to bloat than others. Bloat was effectively controlled on alfalfa pasture by feeding Sudan hay in the corral or in the pasture. The results from feeding alfalfa hay varied greatly, depending upon its coarseness. Pasturing on Sudan at night before placing the cows on alfalfa pasture, appears to be an effective means of controlling bloat.