The term ultratrace elements, often used to indicate elements with an established, estimated or suspected requirement generally indicated by microgram/, could be applied to at least 20 elements. The quality of experimental evidence for nutritional essentiality varies widely for the ultratrace elements. Thus, although differing dietary guidance is appropriate for these elements, most need increased attention in future editions of the Recommended Dietary Allowances (RDAs) for the following reasons: (1) Increased interest in these elements by the public has been stimulated by the mass media; thus, responsible information about the usefulness of the ultratrace elements for health and well being is needed. (2) Risk assessments and toxicological standards are influenced by the RDAs. Authorative advice is required to prevent standards that obstruct the achievement of beneficial intakes of ultratrace elements. (3) An emerging new paradigm is that the determination of nutritional requirements should include consideration of the total health effects of nutrients, not just their roles in preventing deficiency pathology; some of the ultratrace elements have identified health benefits. Six ultratrace elements, iodine, selenium, manganese, molybdenum, chromium and boron (and cobalt as vitamin B12), merit specific RDAs. The term "estimated safe and adequate daily dietary intakes (ESADDI)" should not be used for any of the other ultratrace elements because of the misleading words "adequate" and "safe". "Apparent beneficial intake (ABI)" seems more appropriate for the elements with beneficial, if not essential, actions that can be extrapolated from animals to humans; these elements include arsenic, fluoride, lithium, nickel, silicon and vanadium. The evidence is too limited or controversial for the remaining ultratrace elements to even provide an ambiguous ABI. The amount found in a healthful diet probably should be a value provided for an appropriate intake for aluminum, bromide, cadmium, germanium, lead, rubidium, and tin.