Complex diseases are due to an interaction of genetic background and environmental impacts. Sensitivity to environmental chemicals varies across the lifespan but the developmental period is uniquely sensitive to environmental chemicals, especially those with endocrine activity. Data from animal studies show that developmental exposures to low levels of a variety of environmental chemicals can cause diseases later in life, long after the exposure is gone. Indeed developmental exposures to a single environmental chemical at low environmentally relevant doses has been shown to result in increased incidence of obesity/diabetes/metabolic syndrome, infertility, premature puberty, attention deficit/hyperactivity, learning disabilities, cardiovascular disease and neurodegenerative diseases...the major diseases of our generation. This paradigm, the developmental basis of disease, changes the focus from intervention to prevention and from the adult to development as the time to reduce disease incidence. It also focuses toxicity testing on low dose developmental exposures and examination of disease incidence later in life. To protect human health we need to reduce exposure to environmental chemicals especially during pregnancy and the first few years of life and this is where Green Chemistry can play an important role...to design and produce a new generation of materials that are inherently safe. Progress in Green Chemistry promises to improve human health and longevity.