The sequencing of the human genome has revolutionized biology and led to an astounding variety of technologies and bioinformatics tools, enabling researchers to study expression of genes, the function of proteins, metabolism, and genetic differences within populations and between individuals. These scientific advances are making an impact in the medical research community and hold great promise for prevention, diagnosis, and treatment of diseases. This developing field also holds great promise for improving the scientific basis for understanding the potential impacts of chemicals on health and the environment. A workshop sponsored by the International Council of Chemical Associations was held to review the state of the science in the application of genomics technologies in toxicology and epidemiology. Further, consideration was given to the ethical, legal, and regulatory issues and their influence on the direction and application of genomics technologies to environmental health research. Four overarching themes emerged from the workshop: Genomics technologies should be used within a framework of toxicology and epidemiology principles and applied in a context that can be used in risk assessment; effective application of these technologies to epidemiology will require suitable biologic samples from large and diverse population groups at the relevant period of exposure; ethical, legal, and social perspectives require involvement of all stakeholder communities; and a unified research agenda for genomics technologies as applied to toxicology, epidemiology, and risk assessment is urgently needed for the regulatory and scientific communities to realize the potential power and benefits of these new technologies.