More than 380 Chinese adults of both sexes were studied for their total body K and 40K using the National Tsing Hua University whole-body counter. The K values were found to have an average of 1.75 +/- 0.4 g K kg-1 body weight for males and 1.41 +/- 0.1 g K kg-1 body weight for females. The average K value for both sexes was 1.69 +/- 0.4 g K kg-1 body weight. The annual absorbed dose for the average male was calculated to be 0.21 +/- 0.04 mGy and for the average female was 0.17 +/- 0.01 mGy. The average for both sexes was 0.20 +/- 0.04 mGy. The 40K activity per unit body weight varied inversely with slenderness, and total body K varied directly with body-build index.