: A microdiffusion procedure was used with a fluoride ion-selective electrode to determine fluoride levels in 548 hair samples collected in 1995-1997 from children and adults living in the low-risk exposure region of Ci-echanów, Poland. An additional 71 hair samples were collected from elec-trolysis workers with high-risk exposure at an aluminium plant in Konin, Po-land. The mean hair fluoride values for the low-risk population varied from 1.3 to 2.6 µg/g (range <0.5 to 26 µg/g) and showed only small association with presumed exposure levels. Among the aluminium plant workers, the mean values were 403.4 and 2828.1 µg/g (range <113.7 to 5459.8 µg/g), and they ex-hibited a strong dependence on the type of work exposure to fluoride. Be-cause hair samples are easily collected, fluoride in hair is a useful indicator of human fluoride exposure.