The unique characteristics of radon make it very attractive for earth science studies, as it can migrate over large distances within the earth and the atmosphere, be measured with accuracy, and be used as a tracer for many environmental processes of interest. This book presents properties, applications and health aspects of radon. Some of the topics discussed include spatial and temporal variations of soil-radon activity in fault zones, beta and gamma dose assessment due to radon short lived progeny, adverse health effects of radon, geological applications of radon anomalies in groundwater and soil-gas, radon and earthquake forecasting, dynamic assessment of radon source in buildings and influence of water-rock interactions on the presence of dissolved radon in groundwater.