The original purpose of our study was to determine if the detection of chromosomal aberrations in peripheral lymphocytes of children might be used as a biomarker of environmental pollution and life style. We compared the results of cytogenetic analyses performed in children and adolescents in the periods 1984-1993 and 1994-1999, in a total of 3402 subjects. The frequency of aberrant cells (AB.C.) markedly decreased in the period 1994-1999 compared with the period 1984-1993. The decreases in AB.C. were significant in the age groups 7-15 and 16-19 years: 1.63% AB.C. versus 1.14% AB.C. and 2.02% AB.C. versus 1.08% AB.C., respectively (P<0.01). No difference in the frequency of AB.C. was observed in newborns. Based on our experience, we believe that monitoring the spontaneous level of chromosomal aberrations in children over 5 year periods may be used to examine the general changes in environmental pollution in larger geographic areas.