ABSTRACT: The characteristics of polysaccharides isolated from milk and soymilk kefir grains, and the composition of flavor and volatile compounds from soymilk kefir were investigated. Soymilk kefir grains revealed lower polysaccharide content than milk kefir grains, with a polysaccharide profile consisting primarily of glucose and galactose, with the former predominating. The apparent molecular weight of the polysaccharide was estimated at 1.7 × 106 Da. In comparison to nonfermented soymilk, the concentrations of the key volatile compounds for soymilk kefir (such as acetaldehyde, acetone, diacetyl, and ethanol) increased, while n-hexanal concentration decreased. The acetaldehyde level for soymilk kefir was slightly higher, but levels for the other volatile compounds were lower than for milk kefir.