Repeated DNA sequences were used to fingerprint strains of Aspergillus fumigatus isolated from a cow with disseminated systemic aspergillosis, cows with single aspergillosis lesions, calves aborted due to bovine aspergillosis, mothers of those calves, and cattle without aspergillosis. The analysis of the Southern blot hybridization patterns obtained suggested that: (i) the portal of entry of aspergillosis in cattle is the gastrointestinal tract, and (ii) infection of aborted calves is due to maternally derived strains. Cattle from the same farm slaughtered on the same day harbour the same strain, suggesting a contamination from feed material.