The HLA-B*27 group of alleles has been extensively studied due to the association of particular B*27 alleles with ankylosing spondylitis (AS). We describe here an HLA-B*27 allele (B*2712) encoding an antigen that lacks reactivity with B27 monoclonal antibodies (moabs) and alloantisera but reacts with some B40/B60 moabs and alloantisera and expresses the Bw6 public epitope. This allele was discovered by the segregation of an HLA-B allele undetectable by PCR-SSP within a Caucasian family from the British population referred for routine bone marrow transplant HLA typing and found in the haplotype A*29; B*2712; Cw*1203; DRB1*13; DQB1*0603. Serological typing showed a lack of reactivity with four B27 moabs and four alloantisera but positive reactivity with moabs and alloantisera specific for B40/B60 and Bw6 public epitopes. Subsequent sequencing showed the closest homology was with B*2708 with three mismatches in exon 2 at positions 204, 209 and 210. The intron 2 sequence was identical with other B*27 lineage alleles including a 2 base pair deletion at positions 95 and 96. The relationship between HLA-B*2712 and reported B60 associations with susceptibility to AS remains to be determined.