Concentrations of the trace metals Cu, Fe, Mn, Ni, and Zn in the ocean have been measured by the new analytical technique of atomic absorption spectroscopy. The method is probably the most sensitive and simplest available. Concentrations of a part in ten billion and less can be measured in a few seconds using less than a cubic centimetre of ocean water directly as it comes from the sampling mechanism. Results are reported from a number of positions and depths in the Atlantic and Pacific Oceans. The following concentration ranges were observed in μg-atom/l. units: Cu 0.018-0.035; Fe 0.10-0.13; Mn 0.054-0.080; Ni 0.0022-0.0063; Zn 0.0091-0.011.