Perchlorate is a chemical pollutant that inhibits iodide uptake and may possibly impair thyroid function. Our previous study found widespread perchlorate exposure in non-pregnant, non-lactating, healthy women residing in Istanbul. The aim of this study is to assess the relative amounts of perchlorate exposure attributable to consumption of municipal water, bottled water and boxed milk available in Istanbul. Only trace levels of perchlorate were found in treated municipal water (58 % detectable, mean = 0.13 A mu g/L, maximum = 0.75 A mu g/L) and bottled water (7.4 % detectable, mean = < LOD, maximum = 0.19 A mu g/L). Conversely, all 30 boxed milk samples contained measurable levels of perchlorate (mean = 4.53 A mu g/L; maximum = 6.21 A mu g/L). Median perchlorate exposure attributable to water and milk (0.007 A mu g/kg/day) is small compared both to the reference dose (0.7 A mu g/kg/day) and to total perchlorate exposure (0.13 A mu g/kg/day) in Istanbul. Therefore, additional studies are needed to identify the major sources of perchlorate exposure in Istanbul.