The calculations prove that average serum lead level in children residents of cities with low environmental lead content approximates 10 mg/dl. This value in cities with high environmental lead content could be nearly 2 times higher and equals 18.9 mg/dl. The main lead sources influencing serum lead levels in children are mainly foods, the soils with dust, polluted air and drinkable waters play minor roles. The estimates show that nearly 400,000 children require medical examination and repeated measurements of serum lead levels, 10,000 children may need specific therapy.