More than 10 years ago, the Radiation Protection Research Programme of the Commission of the European Communities initiated and supported research to understand better the impact of natural radioactivity and, more especially, radon. In the present 1990-1991 programme, emphasis is given to the study of parameters and processes underlying the level of exposure to radon with the aim of increasing our understanding of the physical and biological processes and to develop practical and cost-effective remedial actions. The recommendations of the Commission and radon control policies in the Member States will also be presented and discussed.