Lead, cadmium, and mercury concentrations were determined in breast milk of Saudi lactating mothers from Riyadh and Al-Ehssa regions in Saudi Arabia who were not occupationally exposed. The mean levels for cadmium, lead, and mercury were 1.732 microg/L, 31.671 microg/L, and 3.100 microg/L, respectively. In contrast to mercury, mothers living in the Al-Ehssa region had significantly higher cadmium and lead concentrations in their breast milk than those in the Riyadh region. The estimated weekly intakes of cadmium, lead, and mercury of breast-fed infants in this study were in some cases higher than the Provisional Tolerance Weekly Intake (PTWI) recommended by FAO/WHO, which pose a threat to their health. This necessitates the urgent need to undertake a comprehensive study to determine the sources of exposure to these heavy metals. Breast-feeding is of great beneficial value for the infant's development; therefore, efforts should be made to prevent its contamination with environmental pollutants.