Within the framework of the IGA grant. 1324-3, Ministry of Health, Czech Republic the authors assessed the urinary fluoride concentration in 1491 children from 10 localities in the Czech Republic ( the submitted results are the fifth part of the final report from 1995). The various localities differed as to their fluoride history. The children lived in these localities from birth. In nine places 12-year-old children were examined, in one all children attending elementary school (Chlum nr. Třeboň - small number of 12-year-old children). In addition to assessment of the urinary fluoride concentration in the children the DMF and DDE index [8, 10] was recorded. Assessment of urinary fluorides was done by the direct potentio- metric method using a pair of electrodes: by an indication ion selective fluoride and a reference calomel electrode. The mean concentration of urinary fluorides in the whole group was 0.623 mg/l; (to obtain ppm values the figure is multiplied with the density expressed in g/ml). In different localities it varied between 0.496 in Strakonice and 0.961 in Ostrava. In 1993 when the investigation was implemented in the Czech Republic no endogenous fluoride prevention was used (drinking water was not fluoridated, no fluoride tablets were distributed). From this aspect the investigation provides comparable material for investigation of the development of fluoride exposure in children.

        Key words: exposure to fluorides – urinary fluoride excretion – fluoride caries prevention