AbstractTrace amount of mercury in human hair has been determined by destructive neutron activation analysis.It was found that the contents of mercury in the hair of normal people in Taiwan area is the order of 6ppm. It is of interest to point out that very little fluctuation is observed in the contents of mercury in human hair regardless of sex and age of the normal people under investigation.On the other hand for those people who are working in the caustic soda manufacturing plant in which mercury is used as cathode in the electrolysis process of saline water, the mercury contents in their hair are definitely much higher (ca. 30 times) than the average values of normal people.