The retinoid system is involved in growth, differentiation, homeostasis, and survival of the developing embryo, juvenile, and adult. Genetic programs for organ shape and structure formation, such as the neural tube, heart, limbs, and face, are under control of the retinoid system, as are sex determination, fertility, neurodevelopment, and vision. Considering these key roles in cell biology and physiology, it has become apparent that the potential for toxicity to the retinoid system needs to be captured by internationally harmonized regulations. The possibility to develop molecular effect biomarkers based on the retinoid system for toxicity screening and monitoring studies was pointed out in the Detailed Review Paper (DRP) 178 of the OECD Test Guidelines Programmea. The potential to provide mode-of-action information for critical end-points in existing test guidelines was also noted, and a DRP on the retinoid system was initiated (project 4.97b) within the OECD Endocrine Disruptors Testing and Assessment Advisory Group (EDTA AG). This regulatory interest in the retinoid system encouraged Reproductive Toxicology to initiate a Special Issue to provide its readers with up-to-date state-of-the-art information on the topic, and to support the retinoid system work of the OECD. The Special Issue will cover the broad scope of retinoid biology in health and disease, as well as the impact that different categories of chemicals might have on these processes over the life course. The Special Issue will stimulate cross-fertilization between the many knowledge domains involved with retinoid system research on the one hand, and research in endocrine and reproductive toxicology on the other hand. Submissions of original research, current reviews, commentaries, case reports and other information are all welcome. ahttp://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/jm/mono(2012)23&doclanguage=en,
b http://www.oecd.org/chemicalsafety/testing/oecd-guidelines-testing-chemicals-related-documents.htm; go to Current Work Plan