Indoor radon concentrations at METU, CIG-DEM and DOSTLAR in Ankara were measured using electrets. The statistical analysis of the data indicated a lognormal distribution of radon concentrations, with no significant difference between CIGDEM and DOSTLAR with geometric means of GM = 87.5 and 54.5 Bq m(-3), respectively. Radon concentrations did not change seasonally at CIGDEM which contain modern buildings, but at the slum district DOSTLAR, with poor insulation of houses a seasonal variation was observed. Annual effective radon doses were estimated (0.4-8.4 mSv). Public awareness about indoor radon was raised.