HLA-B27 associated rheumatic syndromes have been found in 13% of more than 200 pacemaker treated Caucasian men. Furthermore, a significantly increased frequency of HLA-B27 was found in pacemaker treated men without HLA-B27 associated rheumatic disorders. Consequently, an HLA-B27 associated disease process seems to be the cause of heart block development in 15 to 20% of Caucasian pacemaker treated men. The purpose of our study was to find out if the HLA-B27 associated disease process was equally common in pacemaker treated women. Eighty-five pacemaker treated women with second and third degree heart block were HLA typed for B27, and HLA-B27 positive individuals were further examined for the presence of associated rheumatic disorders. HLA-B27 was present in 7 women, 8.2%, similar to the frequency in the general population, and none of them had an associated rheumatic disease. Thus, there is a significant sex linked difference in the susceptibility to HLA-B27 associated heart block.