Combustion of coal is a significant source of technologically enhanced exposure to naturally occurring radionuclides. Coal, like most materials found in nature, contains natural radionuclides and their products in small quantities. Therefore, depending on the activity concentrations of naturally occurring radionuclides in coal, a coal-fired power plant might potentially contaminate its environment. In the present work, from the point of view of environmental contamination, indoor Rn-222 concentrations in 100 houses located in the vicinity of Yatagan coat-fired power plant (YaCPP) in the southwestern part of Turkey were measured by solid state nuclear track detectors (LR 115-II). The time-integrated Rn-222 concentrations in the houses ranged from 10 to 120 Bq m(-3). This corresponds to an annual effective dose equivalent ranging from 0.6 to 7.3 mSv. It was also derived from the observations that, in 96% of the homes, a Rn-222 concentration of 100 Bq m(-3), taken as the limit for future buildings, as recommended by ICRP (1984), was not exceeded. (C) 1999 Elsevier Science Ltd. All rights reserved.