Five overlapping segments of the VP60 capsid protein gene of rabbit haemorrhagic disease virus have been expressed in E. coli under the control of the T7 RNA polymerase. After purification, the antigenicity of these denatured protein segments has been studied by reactivity with sera from both naturally infected and vaccinated animals in Western blot analysis. The amino terminus segments of the protein (comprising the first 175 amino acids) are highly reactive with the tested sera, between 10 and 100 fold more than any of the segments reproducing the carboxy half of VP60, which is believed to be solvent-exposed in the virus particles. These results strongly suggest that the antigenic structure of the carboxy moiety of VP60 is mainly based on conformation-dependent B-cell epitopes whereas the amino terminal region of VP60 contains continuous antigenic determinants for the immune response elicited during both virus infection and exposure to the inactivated vaccine.