The question, whether HLA-B27-negative patients with classical ankylosing spondylitis (AS) belong to a separate nosological entity, was studied by a standardized analysis of 12 clinical, 8 radiological and 6 laboratory criteria in 95 cases, including 7 with HLA-B27-negativity, who reinforced international criteria for classical AS. The results showed neither definite clinical nor radiological, or laboratory differences between the HLA-B27 negative and positive group. We conclude, that existence or absence of the tissue antigen HLA-B27 has no influence on inflammatory activity of skeletal or soft tissue manifestations of the disease. The group of HLA-B27-negative patients who fulfill the criteria of classical AS does therefore not seem to form a separate nosological entity.