HLA antigens were studied in three different groups of 50 patients each. These included (a) Forestier's disease, (b) ankylosing spondylitis, and (c) polyarthrosis of the hands. HLA typing included 12 specificities from locus A and 15 from locus B, the frequencies being compared to those in 700 normal controls. No significant differences were found in the frequency of distribution between the polyarthrosis patients and the normal population. In patients with Forestier's disease, B5 was increased, but this was not a significant difference. The antigen B27 was present in 94 per cent of patients with ankylosing spondylitis, confirming previous studies.