Environmental policies in Mexico have contributed to the reduction in the production or use of some persistent organic pollutants (POPs) and metals. However, monitoring of POPs concentrations in humans living in hot spots is lacking. Therefore, the objective of this study was to conduct a screening for POPs and metals first in Mexican children living in high-risk areas. During the year 2004, we analyzed a total of 229 healthy children (aged 6-12 years old) who resided in communities located in nine Mexican states. Organochlorine insecticides, PCBs and metals were quantified in plasma and urine samples. We detected p'p-DDE in all the children; moreover, p'p-DDT, lindane and hexachlorobenzene were detected respectively in 14%, 85% and 10% of the children studied. Measurable levels of PCBs were recorded in only one community, where six of 14 PCB congeners assayed were detected (numbers 52, 118, 138, 153, 170 and 180). All the children had detectable levels of lead in their blood (mean level, 4.6 microg dL(-1)); furthermore, 57% of the children studied had levels higher than 5.0 microg/dL. The mean level of urinary arsenic (UAs) for all the children was 22.35 microg g(-1) creatinine and 15% of those children had concentrations of UAs above 50 microg g(-1) creatinine. For cadmium, the mean urinary level was 0.78 microg g(-1) creatinine, and only one percent of the children had values above 2.0 microg g(-1) creatinine. The results cannot be generalized since the communities selected are not representative of the Mexican population; however, they indicate that Mexican children are exposed to chemicals and some at risk levels.