Radon and thoron is a radioactive gas that emanates from rocks and soils and tends to concentrate in an indoor environment. Soil gas infiltration is identified as the most important source of residential radon. Other sources, including building materials and water extracted from wells, are also important in some circumstances. Radon is one of the major contributors to the ionizing radiation dose received by the general population. The dose due to radon and thoron are mainly delivered by their decay products which tend to get deposited in the respiratory organs of humans during breathing. In this study the measurement of radon, thoron and their daughter products concentration were carried out in the residential houses of Shahjahanpur, Uttar Pradesh, India using solid state nuclear track detector (SSNTD). The measurements were made in residential houses in the indoor environment of Shahjahanpur, using a twin chamber radon dosimeter. In the present study, it is found that the average value of radon and thoron concentration varies from 18.77 Bq/m3 to 44.95 Bq/m3 and 10.89 Bq/ m3 to 21.20 Bq/m3 respectively while the average value of radon progeny and thoron progeny concentration varies from 2.02mWL to 4.85 mWL and .29 mWL to 0.57 mWL respectively. The observed value of radon, thoron and their progeny concentration inside the dwellings were found to be lower than the ICRP value of 200 Bq/m3 and thus are within safe limits.