The aim of our study was to evaluate any effects in red blood cells in children exposed to air pollution. The subjects were 354 pupils, aged 11-14 years, living for more than ten years in the same home. The exposed group of children (n=215) were attending school in a city area with a high level of air pollution, while the children in the comparison group (n=139), designated the non-exposed group, were attending school in an area with a lower level of air pollution. The mean value of hemoglobin (g/mL) for exposed children was 10.97 ±0.38 and for non-exposed children 11.09 ±0.78. The diagnosis of iron deficiency anemia was made using the pre-defined criteria. The air concentrations of black smoke, nitrogen dioxide, sulfur dioxide and lead in sediment matter were determined from 1990 to 2000. The red blood cell count and average of hemoglobin blood levels of exposed children differ significantly from those of the non-exposed (P<0.001). There was also a significant difference in the prevalence of anemia in children exposed to higher concentrations of air pollutants (RR =3.76; 95% CI:2.06-6.88). These findings suggest that air pollution could have negative effects on red blood cells in children.