The causative rabbit haemorrhagic disease viral antigen (RHDV) was purified by sucrose and caesium chloride density gradients. The viral fractions were characterised by a haemagglutination test and a dodecylsulfat polyacrilamide gel electrophoresis (SDS-PAGE). Different migration patterns were observed after sucrose and caesium chloride (CsCl) density gradient centrifugations.