The object of this research was to determine if the isotope ratios of lead were significantly different in various environmental media and if such differences could be used to distinguish the lead in the media. Significant differences in the lead isotopic ratios in rock and soils, grasses, tree leaves and tree rings, air particulate, and in some industrial products such as coal, fly ash, gasoline, and fuel oil have been found.Leaf, grass, and soil samples taken across the New Jersey Turnpike showed a change in lead isotopic ratios from the Turnpike to a point one mile to windward. The mean value of the Pb-206/Pb-204 ratio in topsoil within 500 feet of the Turnpike was 18.2 ± 0.2 and beyond 500 feet was 18.7 ± 0.15. Lead sampled from soil profiles in two forested locations in northern New Jersey showed an increase in Pb-206/Pb-204 ratios, with depth from 18.7 to 19.9 in a 30-inch profile. The lead abundance decreased from 47.5 to 12.0 p.p.m. The mean ratios of Pb-206/Pb-204 from coal and gasoline analyzed were found to be 18.8 ± 0.2 and 18.3 ± 0.3, respectively. The mean value for the same ratio in the published data on coal is somewhat higher. Fly ash and the coal from which it came both contained lead of the same isotopic ratio.Before stating the purpose of this research, let us point out that large variations in lead isotopic ratios, as much as a factor of two, exist in the rock strata and mineral deposits of the world. Industrialized countries use large ton-'Department of Geology, King's College, Briar Cliff Manor, N.Y. nages of lead annually. In an average recent year, the United States alone consumed 1.1 million tons (U.S. Bureau of Mines Minerals Yearbook, 1966).