Asbestosis is interstitial lung fibrosis due to inhalation of asbestos fibres. Up to the ban of import in 1986, 0.7 mil tons had been used in Denmark. The diagnosis of asbestosis is a challenge because of long latency time and very few national occupational asbestos measurements. The cornerstone of exposure assessment is a thorough occupational history, investigation of asbestos content in products used, search for possible and relevant measurements of asbestos fibres in the air, and results of lung biopsies, if present. Although no definite lower limit of exposure can be defined, a cumulated exposure of > 10 fibre-years is a relevant measure for exposure defining the disease, as one fibre-year equals one asbestos fibre/cm3 air/occupational year.