This equine infectious anemia virus (EIAV) immunodiffusion (ID) test detects precipitating antibodies in sera of Equidae to purified recombinant EIA virus core protein of 26,000 molecular weight (p26). Sample sera, if positive, will form a line that fuses with reference positive control lines or that deviate the reference positive control lines inward near the sample well without formation of a visible line. Negative sera will neither form a line that fuses with the reference positive control line nor cause deviation of the reference positive control lines.