The present study was carried out to measure the risk of ambient gamma radiation to the general public by measuring indoor radon and thoron activity concentrations in dwellings around Bababudan schist belts of South Karnataka, India. The study area is surrounded by old granites, younger granites, metabasic, schist and genesis type of rocks. The measured radon and thoron concentrations in dwellings ranged from 44.44 to 85.62 Bq m-3 and 17.78 to 46.67 Bq m-3 with geometric mean values of 63.51 and 29.33 Bq m-3 respectively. The estimated total annual effective dose from radon and thoron ranges from 1.55 to 3.33 mSv y-1 with an geometrical mean value of 2.43 mSv y-1. The current study shows that the annual effective dose that residents of the study region receive is less than 3-10 mSv y-1, the level of radiation exposure that the International Commission of Radiological Protection recommends and that they are safe from exposure to radon, thoron, and their progenies.