The DNA sequence of bovine herpesvirus type 1 (BHV-1) ST strain (BHV-1.2 subtype) entire unique short (US) region and part of adjacent flanking sequences of the inverted repeats was determined. The BHV-1 ST US region is 9745 bp in size and has a 70.5% G + C content. Eight potential open reading frames (ORFs) longer than 100 amino acids and designated ORF1 to ORF8 were identified on this sequence. Seven of these had counterparts in the US of herpes simplex type 1 (HSV-1), pseudorabies virus (PRV), and equine herpesvirus type 1 (EHV-1). BHV-1 ORF2 encodes a protein homologous to HSV-1 US2; ORF3 putative protein exhibits homology with HSV-1 US3 (serine-threonine protein kinase); ORF4 encodes a putative glycoprotein homologous to PRV gG (gX) and EHV-1 gG (gX); ORFs 5,6, and 7 encode respectively HSV-1 glycoproteins gD, gl, and gE homologues; and ORF8 codes for a putative homologue of HSV-1 US9. Although BHV-1 ST strain apparently lacks a HSV-1 US1 homologue, the genetic content and the genomic organization of its US region was found to be similar to the general organization already described for HSV-1, EHV-1, PRV, and avian herpesviruses HVT and MDV US regions. In fact, the BHV-1 US region genomic organization is the closest to the general consensus determined from the comparison of known alphaherpesvirus US regions.