The role of oxidative stress and antioxidants in the field of human toxicology is increasingly gaining attention. Intracellular levels of reactive oxygen species (ROS) can impact differentiating cells, e.g., normal stem and precancerous cells, and elevated ROS levels can also cause damage to biomolecules. Both foreign (xenobiotics, e.g., natural antioxidants and toxicants such as quinones) and endogenous substances and metals (e.g., iron) affect ROS levels and play roles in disease development. "Oxidative Stress in Human Toxicology" consists of twelve papers (nine original articles and three reviews) written by an international board of authors where exposure to xenobiotics is a common denominator. The reprint covers recent developments in the field of oxidative stress related to human toxicology with suggestions of novel mechanisms of action and hypotheses based on findings in clinical (human), in vivo (animal), in vitro (cell culture), and in chemico studies.