Abstract: One hundred and sixty-six patients with different forms of rheumatic diseases were tissue typed for 26 antigens of the A and B locus of the HLA system, using a modified KN cytotoxicity test. Among 25 patients with confirmed ankylosing spondylitis, 23 had HLA B27 (92 per cent), compared to 2.5 per cent in the normal controls. This confirms the strong association of HLA B27 with ankylosing spondylitis. Eight patients had ...