The dsRNA viruses represent a large, diverse group of pathogens (affecting a very wide range of host species), several of which are of medical, veterinary or agricultural importance. Many of the icosahedral dsRNA viruses show striking structural and functional similarities that reflect the similar problems that they face replicating their dsRNA genomes while avoiding the dsRNA activated defence mechanisms of their host species. These similarities appear to indicate a common if distant ancestry that is not always evident simply by comparison of nucleotide or amino acid sequences. To facilitate the identification and comparisons of cognate proteins from different species, genera and families of dsRNA viruses, a series of tables were originally constructed for the 7th International Symposium of dsRNA viruses held in Aruba in 2000. These have now been updated and extended (for the 8th Symposium, held in Tuscany 2003) and are available from the dsRNA virus website at.