The nucleotide sequence of a region of DNA 30 kb from the right end of the orf virus genome has been determined. Examination of the sequences revealed an open reading frame encoding a 10K peptide with significant amino acid homology to the 14K 'fusion' protein reported in vaccinia virus. The orf virus sequence has a 31% identity with the vaccinia virus protein, but a higher level of homology of core predicted residues. The secondary structure of both proteins is also similar. The occurrence of the TAAAT sequence upstream from the initiation codon indicates that the sequence is likely to be transcribed late in infection.