The detenmnation of optimal nutritional status has traditionally been based upon generalized parameters such as weight gain and body fat levels. Vitamin and mineral requirements were often related to the intakes needed to prevent overt signs of deficiency diseases such as beriberi or scurvy. However, in the past decade or so, there have been intensive investigations to determine the subtle changes in physiological functions associated with marginal micronutrient intakes. There is a growing consensus that immune system activities are very sensitive indicators of micronutrient status. During this decade, there has also been a rapid expansion of research in the role of free radicals and antioxidants in the major chronic diseases which afflict mankind( i.e. cancer, cardiovascular disease,and autoimmune disease). The main function of antioxidant nutrients in an appropriate diet is the prevention of oxidative damage to cells and their physiological functions. Antioxidant nutrients counteract free radicals and damaging oxidative actions on cell membranes. Since the cells of the immune system are rapidly differentiating and proliferating, such dividing and transforming cells are particularly susceptible to damage by oxidation. The interactions of antioxidant nutrition and immune system activities and disease resistance are therefore logical areas for research. Thus, the objective of this symposium was to bring together the leading investigators who have examined the immunological effects of dietary essential nutrients which share the capacity to act as antioxidants.