Diffuse idiopathic skeletal hyperostosis (DISH) is a skeletal disease characterized by ligamentous ossification of the antero-lateral side of the spine. The prevalence of DISH was studied in a cross-sectional, population-based study of Hungarian men and women, 50 years and over. The study was based on an analysis of the lateral thoracic and lateral lumbar radiographs of 635 persons recruited from a population register in Budapest, Hungary. Radiographs were taken according to standardised protocol and DISH was classified using the Resnick and modified Resnick criteria. The prevalence of hyperostosis according to the modified Resnick criteria was 27.3% in men and 12.8% in women. There was an increase in the prevalence of DISH with increasing age in men, from 10.0% in the 50-54 year age group to 36.6% in those over 75 years, and in women from 1.9% to 25.9% in the same age groups. According to this radiology survey the disease is more frequent and more severe in men than in women throughout life.