More than 80,000 chemicals are registered for use in the United States and the impact of many of these chemicals on public health is unknown (1). However, safeguarding public health depends on identifying the potential toxic effects of these chemicals and the levels of exposure at which they may become hazardous to humans. In the late 1970s, interest arose within the Department of Health, Education, and Welfare for the creation of a centralized and coordinated effort for the research and testing of chemicals of public health concern. In response, Joseph A. Califano, Jr., Secretary of Health, Education, andWelfare [known today as the Department of Health andHuman Services (DHHS)] established the National Toxicology Program (NTP) within the Public Health Service in 1978. NTP was created as a cooperative effort to improve coordination and integration of toxicology testing activities across the federal government, provide needed information to regulatory and research agencies, develop and validate improved testing methods, and strengthen the science base in toxicology. David P. Rall, who was Director of the National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health (NIH), was designated to also serve as the first NTPDirector (2). Secretary Richard S. Schweiker granted permanent status to the NTP in October 1981 (3). The need for a program like the NTP arose because of increasing scientific, regulatory, and congressional concerns in the 1960s to 1970s about

the human health effects of chemical agents in our environment. Many human diseases were thought to be directly or indirectly related to chemical exposures; therefore, it was thought that decreasing or eliminating human exposures to those chemicals would help prevent some human diseases and disabilities (4).