Retinol (vitamin A) and its natural metabolites, which are derived from carotenoids in plants, are essential micronutrients for embryonic vertebrate development as well as for most cells throughout life. Fruit and vegetables do also contain many other bio active substances collectively called phytochemicals. There exist convincing evidence that diets high in vegetables and fruit decrease the risk of cancer in a number of other organs, and that phytochemicals such as antioxidants may be responsible for the beneficial effects. Given this fairly unique situation having components of fruit and vegetables as major cellular regulators, a research project that studies the metabolism and function of vitamin A and such phytochemicals has been initiated. As both vi tamin A and many phytochemicals efficiently regulates gene expression in cell cultures, but much less is known about the role in living organism, the project will now develop techniques enabling it to assess their role in intact organisms like mice, and h ealthy and diseased humans. The aim is to develop oxidative stress biomarkers allowing to assess the effect of phytochemicals in fruit and vegetables in normal individuals and selected groups of cancer patients. Increased knowledge in this field is likely to be beneficial not only for understanding of major aspects of normal function, but also for treatment of some forms of cancer.