A systematic measurement of radon/thoron concentration by using pin-holes dosimeter and their decay products by deposition based progeny sensors have been carried out in indoor environment of district Palwal, Southern Haryana, India. LR-115 type-II of cellulose nitrate with thick polyester base film was used as detectors. A total 150 locations were selected for measurements over a period of 40 days. In this paper, results of winter season are reported and compared with results of summer and rainy season. The measured average indoor thoron gas concentration (34.6 ± 1.5) is about 3.5 times higher than the world average value (10 Bq m.sup.-3). The average values for radon concentration, EERC, and EETC is found below the world average values of 40 Bq m.sup.-3 for radon, 15 Bq m.sup.-3 for EERC, and 0.5 Bq m.sup.-3 for EETC. The average annual effective dose inhaled by humans was estimated and compared with recommended limits of ICRP and WHO.