Copper is known to be an essential nutrient for human beings, but a Recommended Dietary Allowance has not yet been established. A safe and adequate range of intake was established in 1980 for copper and five other trace elements. The range for copper, 2 to 3 mg/day, is higher than the usual dietary copper intake of many individuals in this country. On the basis of balance studies, a requirement of 1.3 mg/day has been suggested. Recent data on copper intake and bioavailability should aid in reevaluating the dietary copper requirement. Copper deficiency symptoms have seldom been observed in human beings. When copper deficiency has been recognized, it has been under unusual conditions, such as in patients receiving parenteral nutrition. Interactions between copper and other dietary components may alter copper status, but the impact of those interactions is not yet well understood. Dietary factors that may affect the bioavailability of copper include the levels of copper, zinc, and molybdenum in the diet; iron deficiency; ascorbic acid intake; intake of carbohydrates, including fructose, glucose, and starch; and fiber and phytate intakes. Some drugs may also affect copper bioavailability.