In this study, PM10 concentrations, as well as the size distributions of Fe-containing and Cucontaining particles are measured in six subway stations in Istanbul. The average daily PMic, concentrations are found to vary considerably. They were also found to be significantly higher than the levels found at urban air quality stations. Further, the relative abundance of Fe-containing particles among the particles of size >2.1 mu m collected in the metro stations is 3.5-8 times higher than in the in the Istanbul atmosphere. (C) 2011 Elsevier Ltd. All rights reserved.