Radon, a naturally occurring radioactive noble gas, is the main source of the natural radiation that is received by the population. It derives from the traces of radium in rocks and can diffuse directly or as solution in water to the earth's surface. Measurements of radium and radon concentration in a total of ten different well waters sampled at about 100 m depth in the Afyonkarahisar area of Turkey have been made. It was found that the concentration ranged from 0.42-28.82 Bq center dot L-1 for radon and from 0.07-7.16 Bq center dot L-1 for radium. A 99% correlation between radon and radium concentrations was found. From these data the average annual effective dose equivalent from radon and radium in the water have been estimated to about 73.8 and 778.96 mu Sv center dot y(-1), respectively.