This study presents the chemical composition of wet deposition that was collected at four different regions of istanbul, Topkapi, Bagcilar, Maltepe and Goztepe, during the period January 2001-May 2001. Bulk deposition was collected together with the wet deposition at only one station, Goztepe, during the period of January 2001-December 2001. Fifty four wet deposition samples and 21 bulk samples were collected during the study period. The mean value of pH of wet deposition samples for all regions was found to be 5.26. Results indicate that Ca2+ concentration in precipitation was high, as was SO42-, neutralizing the acidity. The mean value of the non-sea-salt fraction in the wet deposition for Ca2+ and SO42- were 98%, 91% indicating that Ca2+ and SO42- were mainly coming from sources other than sea. Difference between bulk and wet deposition of Ca2+ and SO42- was found to be highest. Those differences between bulk and wet samples with respect to the overall concentration (wet+bulk) were lower than 30% for ammonium and nitrate, while the differences of SO42-, Ca2+, Mg2+, Cl-, Na+ vary between 62% and 36%. Higher enrichment factors were found for most ions and higher correlation coefficients were obtained among most of the ions in dry and bulk deposition, in comparison with wet deposition. (C) 2003 Elsevier Ltd. All rights reserved.