Bacterial contents of both the anal gland and castor gland of the beaver (Castor canadensis) were determined. Using our culture methods, no bacteria were isolated from the castor glands, but the anal gland contained high numbers of the aerobeEscherichia coli and the anaerobeBacteroides fragilis. The latter may be represented by several variants but facilities were not available for advanced anaerobic analysis. The relative numbers of each bacterial group and the group present were constant regardless of sex, age class, or colony of beaver. The bacterial fermentation hypothesis is rejected for castor gland section but remains possible for anal gland secretions based on variations seen inB. fragilis. The role of the products of both the castor gland and anal gland are discussed in relationship to scent communication in beaver.