The prevalence of diffuse idiopathic skeletal hyperostosis (DISH) was studied in a hospital based population of African Blacks over the age of 40 years. The study was based on an analysis of the lateral chest radiographs of 1000 patients in a retrospective study and 500 consecutive medical admissions in a prospective study. The overall prevalence of DISH was 3.9% (males 3.8% and females 4.2%). There was a rise in the prevalence of DISH with increasing age from 1% in the 40–49 year age group to 13.6% in those over 70 years. The prevalence of diabetes was 52.4% in the 21 patients with DISH who were seen in the prospective analysis. Ankylosing spondylitis, which is associated ith HLA-B27, is rare in African Blacks. However, DISH is not uncommon but its prevalence is lower than in a similar hospital based study of Jews in Israel.