Lead isotope analysis is an increasingly widespread tool in the study of environmental pollution as Pb isotope compositions do not change during industrial and environmental processes, and always reflect their source origin. In this study we present the results of R-mode factor analysis for associations between chemical elements in Neapolitan soils, combined with the distribution of Pb concentrations and Pb isotope compositions in order to differentiate natural from anthropogenic metal sources. Results show Neapolitan urban soils to be significantly enriched in Pb, Hg, Zn, Sb, and to a lesser extent in Cu, Cd, Cr and Ni. Lead isotope measurements form a trend suggesting mixing between two end-member compositions, one of clear natural origin (geogenic) and another related to human activities (anthropogenic). Lead isotope investigations demonstrate that road traffic is one of the main sources of metal pollution.