A spectrochemical study was made of 66 crude-oil samples from different parts of the United States to investigate the geologic significance of trace metals in oils. Among the oils analyzed, those from some basins contain distinctively different trace-metal suites, but oils from basins of similar age and environment do not show characteristic differences. A detailed study was made of Lower Pennsylvanian oils from the Seminole area, Oklahoma. The trace-element content of these oils did not serve to correlate producing strata from pool to pool or to differentiate producing strata. The areal distribution of vanadium and nickel concentrations in the Seminole area, however, is closely related to paleogeographic trends: the concentrations are greatest near the shoreline and decr ase basinward. The decrease in concentration may be attributed to adsorption of the polar metal-bearing organic constituents during migration or to different metal contents of oils that originated in different parts of the basin.