The Mayo Clinic records linkage facility for residents of Rochester, Minnesota, Yielded 102 cases of ankylosing spondylitis (AS) diagnosed from 1935 through 1973. The incidence did not change significantly over the 39 years. Three times as many males as females were affected. In contrast to another recent report, survivorship of males with AS was not different from that of the general population, whereas survivorship of females with AS was reduced. The overall prevalence was 129/100,000.