This article, by Irene A. Hantman, a legal fellow with the United States Environmental Protection Agency and vice chair, membership, of the American Bar Association Committee on Pesticides, Chemical Regulation, and Right to Know, explores nanotechnology regulatory policy. This emerging technology, she writes, poses a dilemma for policymakers, who are both criticized by industry for going too slow on regulatory approval, and by environmental advocates who say government is not adequately addressing the potential health and environmental risks involved. The article details the framework that governs nanotechnology, and examines the efforts of regulatory agencies in the United States and Europe to assess the risks of nanotechnology. Hantman concludes by saying the tension between the need to test and understand the potential risks and hazards of products made with engineered nanomaterials, and the desire to commercialize such products, is likely to continue: “Companies large and small see great potential for innovation and profit. Environmental and public health groups worry that precautionary measures are inadequate. Friends of the Earth points to ‘public and environmental health disasters that could have been avoided if greater attention had been paid to early warning signs of danger, including asbestos, benzene, PCBs and BSE (mad cow disease).’ Scientists echo this caution. The future will tell the extent to which industry supports responsible development of commercial nanotechnology applications.”