For the different parts of the İçel city, for 100 houses, radioactivity concentrations have been measured at badroom and living room in summer and winter. CR-39 niicleer trace detectors were used in this measurements. According to the results of investigations, it was understood that radon concentration is 22-159 Bq/m3 in summer and 13-59 Bq/m3 in winter. Mean values are found as 23 Bq/m3, and 44 Bq /m3 respectively. in addition, the correlation between radon concentration and its effects on the houses and persons living in these houses were also discussed.