Lead is a ubiquitous xenobiotic metal and because of its widespread industrial use is one of the most serious environmental pollutants. Lead is highly toxic and exposure to even low doses can produce adverse effects on all living organisms. In humans, lead exposure can affect virtually all body systems, resulting in severe health problems. On a molecular level, lead can alter or interfere with the activity of proteins and nucleic acids, ultimately resulting in changes in cell metabolism and physiology leading to pathologic states. Lead can also affect the functions of macromolecules, directly or indirectly, by inducing oxidative stress, which is regarded as a primary factor in pathophysiology of lead exposure.