The Twelfth International Congress of Toxicology was held from July 19–23, 2010, in Barcelona, Spain. The congress had 1,816 registered participants, 1216 abstracts presented (1083 published in Tox Letter and 133 in addenda), 50 sessions (6 plenary lectures, 28 symposia, 7 workshops, 3 days posters in 27 sections, 6 training courses), 150 exhibitors from 64 companies/entities (6 nonprofit entities), 180 invited speakers/chairs/course-teachers. The prestigious Deichmann Lecture was delivered by Manel Esteller, Bellvitge Institute for Biomedical Research (IDIBELL), entitled “Epigenetics: The Last Frontier Beyond Genetics.” Prior to the start of ICTXII, there was a day of continuing education courses. In addition, there was a commercial exhibition and an extensive number of social events were enjoyed. Downloadable details of all relevant Congress information may be found on our website.