For the purpose of obtaining the index that represents the contaminated status due to polychlorinated biphenyls (PCB) in the human body, the authors investigated the contents of PCB in the plasma of 183 subjects who were not exposured to the massive amount of PCB occupationaly in the past. The obtained results were as follows; 1. The mean contents of PCB in plasma were 3.35 $pm$ 1.48 ppb in male and 3.04 $pm$ 1.06 ppb in female. $Cl_4$ and $Cl_3$ were the main isomers in both sexes. 2. The distribution of total-PCB by the age group was showed increasing tendency with the age in both sexes. 3. The tendency of freqyency distribution of total-PCB level were skewed to the higher level in malo and skewed to the lower level in female. 4. There was satistically significant interrelationship between age and total-PCB in plasma in both sexes.