In accordance with the Declaration of the Environment Leaders of the Eight on Children’s Environmental Health (Miami Declaration) in 1997, the Japanese government (the Ministry of Environment, Japan) organized a commission tasked to discuss issues related to the present situation of the environmental health of children (Advisory Commission for Children’s Environmental Health). Epidemiological research on children’s environmental health has been recommended as one of the priority projects by the commission because the effects of environmental factors on children’s health are clarified by only studies using children as subjects, particularly, a birth cohort study, and not by animal experiments. The Advisory Committee of Epidemiological Research on Children’s Environmental Health was established in 2007 and decided to start a nationwide birth cohort study following up children from pregnancy to 12 years old. Under the Advisory Committee, a working group composed of scientific experts, including epidemiologists, toxicologists, obstetricians, orthopedists, and statisticians, was organized in 2008. Pilot studies are going to be conducted in several areas in Japan with the support of the working group. Study hypotheses will also be decided by the working group soon. The full-scale survey will start in 2010.