Indoor radon concentration levels were measured in a number of cities in Jordan using CR-39 based cup dosemeters and were found to vary from 27 to 88 Bq.m-3. The natural radioactivity in soil was also determined. The radon concentration levels were found to be dependent on the 226Ra content in the soil. The average radium equivalent activities in soil were found to be within the limit set by OECD countries but according to the present 1 mSv.y-1 dose limit, Jordanian soil is not acceptable as a construction material.