Three techniques for the diagnosis of mammary aspergillosis in ewes were compared: indirect ELISA to detect the level of anti-Aspergillus IgG in serum, determination of galactomannan (Platelia procedure), and detection of DNA of Aspergillus in serum by a nested PCR. Twenty sera from proven cases of aspergillosis in ewes were positive using ELISA (100%), 80% were positive using PCR, but only 55% were positive using Platelia. All 20 control sera were negative using ELISA and PCR, whereas using Platelia methodology one was positive and the other doubtful. The detection of antibody by ELISA in sera is therefore a reliable criterion for the diagnosis of mammary aspergillosis in ewes. Platelia showed the same deficiencies reported in humans, with the appearance of false positives and negatives. The use of PCR was promising and might have valuable application in human medicine.