The fluoride concentration in urine is commonly used for monitoring fluoride exposure, e.g., in aluminium plants. Hitherto this parameter does not seem to have been related to the actual fluoride concentration in plasma following fluoride exposure. In the present study the fluoride concentration in urine, the urinary excretion rate of fluoride and the fluoride concentration in plasma have been studied in five volunteers after intake of JOmg of fluoride in the form of sodium fluoride (NaF) tablets. In pharmacokinetic analyses of the data calculation of the half-life of fluoride from plasma data and from the urinary excretion rate yielded almost identical results; 5.78 hours (plasma) and 5.11 hours (urine). It was found that plasma fluoride levels were correlated with the fluoride concentration in urine (r =. 7532; n=70), but even more with the urinary excretion rate of fluoride (r=.9651; n=63). The data suggest that plasma fluoride levels or urinary excretion rates of fluoride may give a more correct picture of occupational fluoride exposure than fluoride concentrations in urine.