An increase in heavy metal pollution in the soils of Gebze (Turkey) due to intense industrialization and urbanization has become a serious environmental problem. There are two large organized industrial zones in Gebze; the Gebze Organized Industrial Zone (GOIZ) and the Dilovasi Organized Industrial Zone (DOIZ). The region hosts several industrial facilities which are the main source for hazardous wastes which include paint, plastic, electric, metal, textile, wood, automotive supply industry, food, cosmetics, packing, machinery, and chemicals. Soil samples were collected from these two industrial zones and analyzed for their metal contents. Results of the analysis show that the soils are characterized by high concentrations of Cd, As, Pb, Zn, Mn, Cu, Cr and Hg. Since concentrations of other elements do not exceed the permissible levels, they are not evaluated. Concentrations are 0.05-176 mg/kg of Cd, 10-1161 mg/kg of Cr, 7.87-725 mg/kg of Cu, 1.50-65.60 mg/kg of As, 17.07-8469 mg/kg of Pb, 1.96-10,000 mg/kg of Mn, 29.5-10,000 mg/kg of Zn, and 9-2721 mu g/kg of Hg. Application of factor, cluster and correlation analysis showed that heavy metal contamination in soils originates from industrial activities and heavy traffic which are of anthropogenic origin. Contaminations in soils were classified as geoaccumulation index, enrichment factor, contamination factor, and contamination degree. Integrated pollution index (IPI) values indicate that heavy metal pollution levels of soils collected from industrialization sites are greater than those from distal parts of industrialization. Spreading of hazardous wastes from industrial facilities in the study area via rain or wind is the main source of soil pollution. In addition, traffic-related metal pollution is also observed. (C) 2011 Elsevier B.V. All rights reserved.