Ruthenium, one of the rarest metals of the platinum group, has not previously been investigated in ocean waters and sediments because of its low concentration therein and the lack of sensitive analytical methods. However, the study of ruthenium distribution in the ocean is of interest not only in oceanology but also in geology, geochemistry and cosmochemistry, as it may help in understanding the lithosphere formation processes. We report here the results of ruthenium trace determination in various oceanic environments carried out using a combination of methods including fire assay enrichment and laser photoionization spectroscopy in conjunction with vacuum atomization1. The ruthenium content in the marine environment fluctuates in the range covering 4–5 orders of magnitude: ∼1 p.p.t. (parts per 1012) in marine water, tens of p.p.t. in marine biogenic material, 10–100 p.p.t. in bottom sediments and marine phosphorites, and >1,000 p.p.t. in ferromanganese nodules and the Red Sea metalliferous sediments.