Summary: Concentrations of fluorides in samples of breast milk and urine were determined in a group of nursing mothers living in Prague in 1997–1998. Fluoride level in breast milk was traced as a natural source of fluorides in the infants nutrition. The excretion of fluorides in urine was ascertained as the reflection of the mother’s fluoride intake. The mean concentration of fluoride in breast milk amounted to 0.10 ppm F while the one in urine was twice as high. The breast milk fluoride levels correlated well with those in urine. It can be stated, that the breast milk as a sole source of fluorides in infant’s nutrition is deficite and in the period of full nursing some fluoride supplementation is fully indicated.

        Key words: breast milk – fluorides – urine fluoride excretion