Fermented dairy beverages supplemented with the probiotics Lactobacillus acidophilus and Bifidobacterium lactis containing different concentrations of whey in their formulas (0, 20, 35, 50, 65, and 80%, vol/vol) were processed and checked for pH; proteolysis; levels of glucose, lactose, ethanol, acetic acid, lactic acid, diacetyl, and acetaldehyde; and lactic bacteria and probiotic counts. The results allowed the effect of whey concentration on the dairy beverages to be observed for each of the different parameters analyzed. The degree to which the whey concentration was useful for the microbial cultures, particularly probiotic cultures, appeared to have a limit. In general, dairy beverages processed with different levels of whey in their formulation exhibited good potential as a food matrix for supplementation with probiotic bacteria, with production of characteristic compounds of fermented milk products, such as volatiles and organic acids.9696-100