Biochemical function and biological significance of Cu, Zn and Cr are reviewed briefly. During a longterm perenteral nutrition a depletion of the organism of copper and zinc is to be expected. Therefore, in parenteral nutrition, an early substitution of zinc seems to be usefull. Up to now a similar recommendation for copper cannot be given. As many infusion solutions are contaminated with chromium, there is no need to substitute this element in parenteral nutrition.