The validity of CAMP tests with Staphylococcus aureus and Rhodococcus (Corynebacterium) equi as defined for Listeria identification was revised. This characterization method appeared to be unreliable for two reasons: first, a positive CAMP test with R. equi is not specific for Listeria ivanovii as Listeria monocytogenes (and Listeria seeligeri) give also a clear positive reaction; second, doubtful reactions could be observed with S. aureus when assaying haemolytic and non-haemolytic Listeria strains (possibility of false negative and false positive results; subjectivity of the interpretation). The use of a Microplate technique previously described instead of CAMP tests is proposed for the reliable demonstration of the haemolytic character of Listeria in the routine identification of these organisms.