We recently used degenerate PCR and locus-specific PCR methods to identify the endogenous retroviruses (ERV) in the bovine genome. Using the ovine ERV classification system, the bovine ERVs (BERVs) could be classified into four families. Here, we searched the most recently released bovine genome database with the partial nucleotide sequence of the pro/pol region of the BERV beta3 family. This allowed us to obtain and analyze the complete genome of BERV beta3. The BERV beta3 genome is 7666 nucleotides long and has the typical retroviral organization, namely, 5'-long terminal repeat (LTR)-gag-pro-pol-env-LTR-3'. The deduced open reading frames for gag, pro, pol and env of BERV Beta en- code 507, 271, 879 and 603 amino acids, respectively. BERV beta3 showed little amino acid similarity to other betaretroviruses. Phylogenetic analysis showed that it clusters with HERV-K. This is the first report describing the genetic structure and sequence of an entire BERV.