To develop an enforceable drinking water standard from a health-based reference dose, sources of exposure and relevant exposure factors across the U.S. population must be considered. Human exposures, expressed as an estimated daily exposure, can be used to evaluate the health protectiveness of a range of potential regulatory values, thus providing a scientific foundation on which decisions can be based. Recent evidence points to detectable levels of perchlorate in milk and other foods. The purpose of this article is to estimate human exposure to perchlorate from ingestion of drinking water, human milk, and dairy milk. Drinking-water exposure was based on a range of possible regulatory values, derived from the recently established reference dose. Exposure to perchlorate from the consumption of milk was based on exploratory Food and Drug Administration dairy milk data, and on additional published perchlorate concentrations in dairy and human milk samples. This effort is exploratory in nature due to the limited data available at this time. However, it is anticipated that these exposure estimates and comparison with the current reference dose will stimulate dialogue and research that will advance the risk assessment for perchlorate.