Over the last 2 years, Greek yogurt sales and consumption have grown very rapidly leading to a $2 billion per year industry. The by-product of Greek yogurt manufacture is “acid whey,” in which the industry needs to decide its utilization. For every 3 parts of milk, 1 part of Greek yogurt and 2 parts of acid whey are formed. The probiotics industry is rapidly growing since the health benefits of probiotics are widely known. Typically, probiotic bacteria do not thrive in acidic conditions. In a product such as acid whey, which naturally contains proteins, amino acids and sugars (lactose) that are needed for lactic acid bacterial growth, it will be beneficial to determine if the lactic acid probiotic Lactobacillus acidophilus can survive. The objectives were 1) to manufacture a probiotic acid whey beverage, 2) to determine the growth of the probiotic Lactobacillus acidophilus in the acid whey beverage and 3) to study any changes in pH, viscosity and titratable acidity over 5 wk of refrigerated storage. Plain yogurt was manufactured, and whey was separated from the plain yogurt to yield Greek yogurt and acid whey. Acid whey was batch pasteurized, cooled, sweetened, flavored with pineapple flavoring, inoculated with Lactobacillus acidophilus to 10⁷ cfu/mL and stored at 4°C for 5 wk. The L. acidophilus counts declined from 3.2 × 10⁷ immediately after manufacture to 1.4 × 10³ at wk 3 and 90 cfu/mL at wk 5. There were no changes in pH, TA and viscosity of the flavored probiotic acid whey over storage for 5 wk which is desirable as it indicates product stability over shelf life. L. acidophilus survived in the flavored acid whey, although counts rapidly declined over 5 weeks. This suggests future research on methods to enhance acid tolerance of probiotic L. acidophilus.