Cytogenetic analysis of peripheral blood lymphocytes has been performed in 13, resp. 14 children permanently living in the area with an increased fluorides concentration in the drinking water. The set consisted of 6 boys and 8 girls with the mean age of 13,3 years. The investigation was performed repeatedly, in April and in November 1998. Due to a small number of respondents we tried to analyze 200 mitotic sets in each persons. During the first investigation 2525 cells were assessed, 52 of them (2,06%) were laden with structural (38) or numerical (14) aberrations. Relatively often (38) there were also found some other types of aberrations - e.g. despiralization of chromosomes, centromere shifts or endore- duplications. However, these types of aberrations, in agreement with reference method, were not included into the final number of aberrated cells. During the second check up we analyzed 2400 mitotic sets. In 56 (2,24%) of them chromosome aberrations were found. Different types of aberrations were noted in 25 mitotic sets. Investigation performed proved that the mean number of chromosome aberrationsin childrenof ourset statistically significantly differedandwashigher when compared with the rest of the population. The difference was statistically significant on 5%, or 1% level of statistical significance respectively. The resultsof cytogenetic analysis of peripheral blood lymphocytes thus witness in favour of an increased exposition to genotoxic agents. As all the other genotoxic agents were excluded the presence of increased fluorides concentration in drinking water seems to be the only explanation.

        Key words: fluorids - drinking water - chromosome aberrations