The nucleotide and deduced amino acid sequences of the non-structural (NS) protein genes of bovine respiratory syncytial virus (BRSV) strain A51908 were determined. The NS1 and NS2 genes were 524 and 489 nucleotides long with single open reading frames, encoding polypeptides of 136 and 124 amino acids, respectively. Comparison of the NS1 gene of BRSV with the corresponding sequences of ovine respiratory syncytial virus (ORSV) and human respiratory syncytial virus (HRSV) subgroups A and B revealed 82, 67 and 65% identity at the nucleotide level, and 89, 69 and 68% identity at the amino acid level, respectively. The nucleotide identity of the NS2 gene of BRSV to those of ORSV and HRSV subgroups A and B was 80, 69 and 67% and the predicted amino acid identity was 87, 84 and 83%, respectively. The intergenic sequences of the NS1-NS2 and NS2-N gene junctions of BRSV were determined and found to be 13 nucleotides shorter and 29 nucleotides longer, respectively, than the corresponding regions of HRSV.