Thorium is a natural radioactive element and has numerous applications. The extremely low annual limits on intake of national and international regulations and the extreme difficulties in detecting thorium in the body or excreta makes high demands on the techniques used for the monitoring of exposed workers. In addition, there are problems resulting from a lack of information on the biokinetics of thorium and its radioactive decay products. A programme for monitoring thorium intakes on the basis of new regulations in Germany, is described.