In 2006 there was an outbreak of equine infectious anaemia (eia) in Ireland. This paper describes the use of the diagnosis of clinical and subclinical cases of the disease. In acute cases the elisas and the immunoblot were more sensitive than the agid. In one mare, fluctuating antibody levels were observed in all the serological assays before it seroconverted by agid. Viral rna and dna were detected by rt-pcr and pcr in all the tissues from the infected animals examined postmortem. The pcr detected viral dna in plasma regardless of the stage of the disease. In contrast, the rt-pcr detected rna in only 52 per cent of the seropositive animals tested and appeared to be most sensitive for the detection of virus early in infection. Both pcr and rt-pcr demonstrated potential to detect acutely infected horses earlier than some of the official tests. The serological data suggest that the usual incubation/seroconversion period for this strain of the virus was approximately 37 days but may be more than 60 days in a few cases.