[en] The objectives of this thematic file were, in a first part, to specify modes of propagation and of concentration of radon in buildings, and health-related stakes related to this gas. It also proposes a cartography of the potential presence of radon in France and in Brittany, and recalls the evolution of the regulatory framework. Then, it gives an overview of the current taking into account of this issue by concerned actors (public, building commissioners, building professions), and addresses prevention and remediation methods (building design, air tightness, venting) for new or existing buildings, discusses their efficiency, and illustrates them by returns on experience noticed during a field survey. The contributions to different meetings are reported under the form of slides, and notably address the following issues: research works, approaches to returns on experience and results obtained by different studies, basic data and definitions regarding radon, situation in Brittany (basic diagnoses), technical solutions