The human gastrointestinal system can absorb 30-40% of ingested copper from the typical diets consumed in industrialized countries. Experimental data support the existence of a carrier-mediated transport mechanism with an affinity constant in the micromolar range. Aging probably decreases the efficiency of copper homeostasis, resulting in higher plasma copper concentrations in the elderly. Physiologic differences may account for the higher cupremia of females. Supplements of minerals with similar chemical characteristics could reduce copper absorption. This property has pharmacologic applications in Wilson disease. Manipulation of the fiber content of the diet may have an indirect effect on copper bioavailability by altering the bioavailability of mineral antagonists. Proteins and soluble carbohydrates tend to improve copper absorption and bioavailability by enhancing its solubility and intestinal bulk flow. Organic acids, other than ascorbic acid, or agents that form low-molecular-weight chelates, are likely to have a positive effect on overall copper absorption. Conditions associated with malabsorption of macronutrients and gastrointestinal disease can impair copper uptake and contribute to suboptimal copper status.