The case of a five year old Swiss Braunvieh cow suffering from an acute disseminated mycotic pneumonia caused by an Aspergillus fumigatus infection is presented. The animal had calved one month previously and was admitted to the clinic because of recurrent fever. Clinical findings included a reduced general condition, a rectal temperature of 40.6 degrees C, an increased respiratory rate, coughing and serous nasal discharge. On auscultation increased bronchovesicular sounds and moist rales could be heard. Radiographs of the thorax showed a diffuse interstitial nodular pattern throughout the lung. The cow had to be slaughtered in spite of intensive therapy. Necropsy showed multiple nodules measuring up to 4 mm in diameter covering the entire surface of the lungs. Histology revealed an acute disseminated necrotising bronchopneumonia containing numerous branched, septate fungal hyphae identified as Aspergillus fumigatus. A primary aerogenous infection caused by inhalation of spores originating from mouldy hay or soil was suspected.