Charles M. Auer joined the EPA’s Office of Toxic Substances, before the Toxic Substances Control Act (TSCA) was passed, as an entry level chemist doing screening-level risk assessments. He was the first chair of the Structure Activity Team, which was responsible for developing structure activity relationship (SAR) analysis as a method for evaluating new chemicals. While it was clear to Auer that there was never any question that SAR satisfied the legal requirements of TSCA’s Section 4 premanufacture review, he witnessed several studies to verify the validity of SAR results, including a joint effort between the EPA and European Union in the early 1990s. By this time Auer was Director of the Existing Chemical Assessment Division, where SARs were not as heavily relied upon. As a division director, Auer found it difficult to prioritize existing chemicals, primarily because Inventory Update Rules were not issued to collect changing hazard and exposure information; the EPA attempted other, more voluntary methods to collect data, to varying degrees of success. Auer believes that the Office has been very innovating, adjusting to emerging science on toxicity and applying TSCA while staying within its legal limits, and that the key to an effective toxics program is to be as dynamic as the chemical industry.