HLA-B27 represents a family of closely related antigens. More than six alleles differing in limited number of nucleotide substitution had been described (B2701-B2706). We subtyped HLA-B27 in 76 patients with ankylosing spondylitis (AS) and 1200 Chinese healthy persons of Han nationality. Polymerase chain reaction was designed to amplify specific regions for class I (exon 2 and 3). Amplified sequences were tested with eight sequence-specific oligonucleotides to distinguish all HLA-B27 subtypes. The results showed: the HLA-B27 was closely related with AS and at least four subtypes existed in Chinese patients. B2704 was the most common subtype occurring in 54.8% and 50.85% respectively in HLA-B27 positive AS patients and healthy controls. The main HLA-B27 subtypes in the HLA-B27 positive patients distributed in similar proportion to that of HLA-B27 positive healthy controls (P > 0.1). We believe that the above results imply that the prevalences of the various subtypes of HLA-B27 vary in different races. The HLA-B27 specific residues that are shared by the subtypes might be involved in the pathogenesis of AS.