Milk-derived peptides with antihypertensive activity have been identified in many types of dairy products from various types of cheese to yogurt.  Previous studies have shown that proteolysis of casein, the major protein in milk, leads to the formation of smaller peptide degradation products with increased bioactivity, including hypotensive properties.  It has been established that the presence of native microflora in raw milk cheeses, including Queso Chihuahua, a cheese variety originating in Mexico, leads to the development of unique flavors.  In addition, the presence of microbes within the cheese matrices also leads to the proteolysis of milk proteins resulting in the formation of smaller peptides with potential bioactivity.  We present work aimed at studying antihypertensive activity contained within varieties of Mexican-style cheeses.  Water soluble proteins were extracted from Queso Chihuahua samples and analyzed for antihypertensive properties.  Samples displaying hypotensive activity were analyzed further by comparing activities to those of known angiotensin converting enzyme (ACE) inhibitors.  Protein mixtures were also analyzed by reverse phase high performance liquid chromatography (RP-HPLC) and mass spectrometry to identify putative peptide sequences corresponding to the active compounds.  These findings will provide insight into the role of bacteria in the production of antihypertensive properties in cheese and other types of dairy products.