Antioxidant status in humans reflects the dynamic balance between the antioxidant system and prooxidants and has been suggested as a useful tool in estimating the risk of oxidative damage. This paper reviews determinants of antioxidant status such as diet including antioxidant nutrient and nonnutrient intake, absorption and bioavailability, dietary components such as polyunsaturated fatty acids and transition metals, food storage and processing, chemical form, chirality and formulation of supplemental compounds and alcohol intake; environmental factors such as pollutants, ultraviolet radiation and smoking; injury and disease, medications and other medical treatments such as radiation; strenuous exercise; and physiological stage or conditions such as those in premature babies and the elderly. It is proposed that, in addition to current focus on tissues, the antioxidant status of digesta should be considered because of its effect on specific tissues and potential health implications.