Spinocerebellar ataxia type 2 (SCA2) is a human neurodegenerative disease caused by mutation in the ataxin-2 gene on human chromosome 12. Ataxin-2 is a protein of unknown function. We identified a new family of proteins designated as ataxin-2-related proteins (A2RPs), with high homology at the nucleotide and predicted amino acid levels. Ataxin-2 and A2RP are proteins highly conserved in evolution with orthologs in mouse, cattle, pig, frog, and plants. A2RP has several isoforms with different C-terminal domains. The longest isoform is composed of 1051 amino acids and has widespread expression in human tissues by Northern and Western blot analyses.