The sensitivity and specificity of enzyme linked immunosorbent assay (ELISA) for the diagnosis of Taenia saginata cysticercosis was studied among laboratory reared experimentally infected calves and conventionally raised naturally infected cattle by using a T crassiceps metacestode antigen. The intensity of the metacestode burden in experimentally infected animals had a direct effect on the first appreciable rise in the spectrophotometric extinction values and also on the progressive elevation of these values during the later stages of infection. The animals harbouring less than 100 metacestodes were the most difficult to detect by ELISA. Serum from sheep infected with Cysticercus tenuicollis showed cross-reaction. Among the naturally infected cattle the sensitivity of ELISA was poor; only 37.5 per cent of the 24 proven cases could be diagnosed. One of the nine cattle harbouring natural infection of Fasciola hepatica showed cross-reaction. Of the 69 animals 4.3 per cent showed false positive reactions.