Development of methods for the diagnosis of viral haemorrhagic disease and the European brown hare syndrome has proceeded at a steady pace over the last few years. The studies conducted by the authors demonstrate that, like VHDV, EBHSV is a calicivirus. The degree of correlation between the two viruses is a key question both for understanding their biology and interpreting the diagnostic results. A discussion of the similarities and differences between VHD and EBHS is followed by the presentation of the latest antigenic correlation results of the two viruses. Considering the absence of culture procedures to isolate either virus, the diagnostic methods discussed in this review are the haemagglutination (HA) test, immune electron microscopy (IEM) and enzyme-linked immunosorbent assay (ELISA) for virus detection, and the haemagglutination inhibition test (HI) and ELISA for antibody detection. The major obstacles, especially for the diagnosis of EBHS, are described; these are represented by morphological, structural and antigenic modifications due to proteolytic degradation. A differential diagnostic method for the two diseases, based on MAb ELISA, is presented. A final conclusion, drawn from the epidemiological analysis of the virological and serological data, is that EBHS and VHD should be considered as two distinct diseases, each caused by its own aetiological agent.