The distribution of radon activity is determined from pre-earthquake data. Analysis using Normal, Gamma, Weibull and Rayleigh distributions indicates that the variation of radon levels in seismically active regions is best described by a normal distribution. It was observed that radon levels would change in compressive fault lines prior to earthquake. Besides that it tended to increase before the earthquake and then decrease towards the time of earthquake occurrences. (C) 2013 Elsevier Ltd. All rights reserved.