For an 8 year period 45 patients with Bechterew's disease were found who had no antigen HLA-B27. 35 of the patients were tested for HLA--A, -B or -C. In 12 patients antigens of the cross-reacting group B27 (B7, Bw22 and B40) were found. In patients without psoriasis antigens B13, B16, B17 which are known to be related to psoriasis vulgaris were found. 9 patients were antigen Cw2 carriers which is in unbalanced linkage with B27. The B27 negative forms present several clinical features: late onset of the disease, slow and favourable course, development of spinal forms only, lack of iridocyclitis and heart lesions.