Abstract: 1200 Chinese adults of both sexes were studied for their body K and ~(40)K using a low background whole-body counter. The K values were found to have an average of 1.84±0.35g/kg body weight for males and 1.60±0.29g/kg body weight for females. The average K value for both sexes was 1.76±0.33g/kg body weight. The annual absorbed dose was between 0.13～0.15 mSv for males and 0.10-0.11 mSv for females respectively. The ~(40)K activity per unit body weight varied inversely with slenderness and total K varied directly with body-build index.