Physical and chemical properties of warm and hot spring waters as well as soil radon concentrations were measured continuously during a 3-year period in the Marmara region; following the devastating I zmit earthquake of 17 August 1999 (Mw = 7.4). Promising and encouraging anomalies in ground radon emanation have been recorded and found to be closely related to seismic activity. The temporal and spatial variations in the soil radon data are presented. The earthquakes with magnitude >4 in the region were correlated with positive radon anomalies. Furthermore, during quiescence (absence of seismic activity) the radon data indicate random walk behavior of radon in soil and show Rayleigh-type probability density function (pdf), however, during the earthquake build-up period, the data show deviations from Rayleigh-type pdf. The radon positive anomalies indicate disturbance of the path of gas movement or gas release pattern prior to earthquakes. However, systematic and consistent anomalies in physical and/or chemical properties of the spring waters have not been detected for earthquakes occurring in the observation period (M < 5.3).