The protein-bound radioiodine percentage and the stability and specificity of the protein fraction of Fasciola hepatica antigen labelled with 115 1 by electrolytic iodination were compared with the data obtained for the same batch of the antigenic fraction labelled by the oxidation procedure using chloramine T. There were no significant differences between the results obtained with the two methods.DiagmJ;is of fascioliasis, oxidation method of iodination, protein-bound radioiodine percentage, stability, iodinated antigen.