The European Union (EU) Bathing Water Directive (2006/7/EC) sets out standards for designated bathing waters which should be complied with by all Member States. Turkey, being a candidate country to the EU, requires heavy-cost investments in achieving approximation with the EU Environmental Acquis. This paper provides a description of the technical measures and investment and operational cost assessment related to the implementation of the Bathing Water Directive in Turkey. Bathing waters are defined as "all running or still freshwaters or parts thereof and seawater, in which bathing is explicitly authorized by the competent authorities, or bathing is not prohibited and is traditionally practiced by a large number of bathers". Since there is no complete registration of bathing waters in Turkey, this study has targeted all coastal agglomerations and designated these as in proximity to "highly-touristic" and "other" agglomerations including the agglomerations in the proximity of six lakes that are popularly used as bathing waters. For each of these agglomerations an assessment of the existing infrastructure has been made. in defining the infrastructural need, two scenarios have been developed. According to Scenario 1, only highly-touristic and touristic places are to receive investment. The suggested further treatment was "disinfection + sea outfall" and "sea-outfall", for highly-touristic and touristic agglomerations, respectively. In Scenario 2, other coastal agglomerations and all freshwater lakes were also included and disinfection has been proposed for these settlements. It appears that the total investment is at around 12.6 million Euros for Scenario 1 and increases to 21.8 million Euros for Scenario 2; whereas the annual operational and maintenance costs are about 0.5 and 0.8 million Euros for Scenarios 1 and 2, respectively. (C) 2009 Elsevier Ltd. All rights reserved.