reproductive and developmental toxicology are complex areas of considerable importance and intense study, not just for the human population, but also for all animal species. Reproductive systems and developing embryos and fetuses exhibit increased risks of adverse effects due to exposure to a broad range of toxicants, from pharmaceuticals to environmental contaminants. New information concerning risk levels, as well as ways to mitigate risk, are gained using in vitro, in silico, and in vivo toxicity models and epidemiological studies. Research about effects of toxicants on the process of reproduction and on developing individuals requires investigation at all levels of scientific inquiry: molecular, physiological and anatomical; and the importance of genetic makeup in response to toxicant exposure is just being realized. Individuals may encounter substances that have potentially harmful effects on reproductive health or the developing embryo and fetus anywhere in the environment, through water, air, soil, dust, food, or consumer products. The ultimate goal of all toxicology research is to utilize reliable and predictive toxicity testing to understand and prevent exposure to potentially harmful toxicants of reproducing animals and humans as well as developing individuals. This Special Issue focuses on reproductive and developmental toxicology.