Four strains of Bifidobacterium longum were grown at pH 5.5, 6.0, 6.5 and 7.0 and evaluated for survival and bile tolerance during frozen and subsequent refrigerated storage in milk. There were no reductions in cell numbers following initial freezing. There were effects for strain, pH and storage for three of the four strains of B. longum du ring storage at 5°C in milk. Bifidobacterium longum S9 was more stable than other strains in that no losses occurred, regardless of pH during growth. Results were variable for strains II, III, and ATCC 15707 grown at the various pH levels. Bifidobacterium longum S9 did not lose bile resistance during refrigerated storage as the other three strains did.