A simple calibration procedure for the Inshas whole body counter for evaluating total body potassium has been adopted. More than 120 Egyptian employees in the Nuclear Research Center (N.R.C.) were studied for their total body potassium (TBK). The potassium values were found to have an average of 2.85 +/- 0.57 g K kg-1 body weight for males and 2.62 +/- 0.52 g K kg-1 for females, which are higher than the recommended value given for reference man by ICRP. The TBK varied directly with body build index and is slightly sex dependent.