The American College of Toxicology (ACT) is offering an advanced course, Advanced Comprehensive Toxicology, to complement Toxicology for Pharmaceutical and Regulatory Scientists course. The 2023 lectures cover detailed descriptions of the principles of toxicology, effects of xenobiotics on organ systems, discussions of specific classes of toxicants, mechanisms of toxicity, risk assessment, and other contemporary toxicological concepts. The content of this course provides information that may be helpful to those seeking certification in toxicology or to those seeking advanced training in toxicology.