We report the identification of Blastomyces dermatitidis by microscopic examination of a direct faecal smear from a dog with pulmonary blastomycosis. A simultaneously obtained faecal culture grew Blastomyces dermatitidis. The fungus was also cultured from a transtracheal sample from this same dog. This report suggests that yeast-phase cells of B. dermatitidis may be recovered in the stool of dogs with pulmonary blastomycosis following transit through the gastrointestinal tract of swallowed infected sputum. Implications regarding the ecology of Blastomyces dermatitidis are discussed.