The total mercury content in the head hair of 87 dental personnel and 210 Seoul citizens as control was determined. 1) The mean value of mercury content in dentists (8.57ppm) was 3.3 times of Seoul male citizens (2.57ppm) and the median of the former (5.92 ppm) was higher than that of the latter (2.39ppm) by approximately 2.5 times. 2) The mean value of mercury content in dental nurses (5.79ppm) was 2.8 times of Seoul female citizens(2.11ppm) and the median of the former(4.62ppm) was higher than that of the latter (1.86ppm) by approximately 2.5 times. 3) The mean value of mercury content in Seoul citizens was 2.29ppm and the median was 1.98ppm. 4) There was no correlationship between the mercury content in the head hair of dentists and the length of dental surgery experience or the frequency of amalgam fiillings per day. 5) The mercury content of Seoul citizens was higher in the male than in the female. 6) It appears more meaningful to employ median values than mean values when the environmental pollution is considered.