Mercury exposure has been reported among users of skin-lightening creams produced outside the United States but not among nonusers in their households. Mercury exposure can result in irreversible renal and central nervous system damage or death. In March 2010, coordinators of a health study notified members of a Mexican-American family in California with four study participants that they had elevated blood mercury levels and also notified the local health department, which in turn asked the California Department of Public Health (CDPH) to investigate. CDPH interviewed the four study participants and a fifth household member and identified unlabeled skin-lightening creams with mercury content measured at 2.0%-5.7% by weight as the likely source of mercury exposure. CDPH also interviewed friends of the study participants in California who had used similar skin-lightening products, and the Virginia Department of Health (VDH) interviewed relatives in that state who had used skin-lightening products. In all, investigators in the two states collected information and urine specimens for 22 persons in five households. The results indicated that 15 persons had elevated urinary mercury concentrations, including nine users of the cream (six with nonspecific symptoms) and six nonusers. Mercury vapor concentrations as high as 50 µg/m3 were measured in spot household locations; however, the overall concentration for each room in all five households was <1.0 µg/m3, considered a safe level. Both health departments advised users and the public to stop using these creams and issued clinical health alerts notifying physicians about this potential cause of mercury toxicity.