Mercury (Hg) concentrations were determined in spot urine samples of populations living in the highland and lowland areas of Bolivia.

The mean levels of the Hg (U-Hg) were 0.43 and 0.34 mugHg/g creatinine in lowlanders and in highlanders, respectively, which did not suggest existence of high-level exposure to Hg in these populations.

In both highlanders and lowlanders, there was a marked difference in levels of U-Hg among different populations.

Several lines of evidence suggested that local dietary patterns resulted in the observed difference in U-Hg levels, although the responsible food items could not be specified.

In most of the populations examined, females showed higher U-Hg levels than males.

Other factors possibly related to the observed geographical differences are discussed.