Increasingly, chemists, whether in industry, academia, or other settings need to understand the basics of toxicology to meet current legal, safety, and regulatory requirements. As has always been appreciated by IUPAC, understanding starts with good terminology. The core work on a “Glossary for chemists of terms used in toxicology” was published by John Duffus 20 years ago 1 and a fully revised and updated version appeared in 2007. 2 It contains about 1200 terms, and has been adopted by the U.S. National Library of Medicine and, in particular, by the ToxLearn modules on ToxNet. ToxGloss is also found at http://sis.nlm.nih.gov/enviro/iupacglossary/frontmatter.html. The revised version is included in the “Encyclopedia of Toxicology, 3rd Edition” to be published shortly.