Abstract: †This study estimates the economic costs associated with childhood diseases and disabilities attributable to environmental contaminants in Washington State, USA, including asthma, cancer, lead exposure, birth defects, and neurobehavioral disorders. The estimates are based on “cost of illness” models that include direct healthcare costs and indirect costs. The estimates are also based on an “environmentally attributable fraction” model which quantifies the proportions of each disease or disability that can reasonably be attributed to environmental contaminants. The study concludes that the annual cost of selected childhood diseases and disabilities attributable to environmental contaminants in Washington State is $1875 million in 2004 $, comprising $310.6 million in direct healthcare costs and $1565 million in indirect costs, and with a range of $1600–$2200 million a year. These estimates are consistent with other studies. Like the previous studies, a significant proportion of the estimated costs can be attributed to lead exposure. This estimate is equivalent to about 0.7% of the total Washington Gross State Product, and the estimated direct healthcare costs are equivalent to at least 0.2% of the total Washington State health expenditures. These costs could be lessened or prevented if exposures to environmental contaminants were reduced or eliminated. This study argues for the need for an ecosystem approach to human health in which the condition of the environment, in terms of exposures to environmental contaminants, must be addressed taking a systemic perspective.