A survey of open-air sites in NW Turkey identified 16 Palaeolithic sites. Analysis of nearly 2000 lithics identified Lower, Middle, and Early upper Palaeolithic (EUP) components. The Lower Palaeolithic is represented by a core-chopper/flake assemblage at one site and an assemblage with small bifaces at another. Middle Palaeolithic assemblages similar to the typical Balkan Mousterian were found at most sites, and an EUP assemblage similar to the Balkan Aurignacian was found on the Black Sea coast. Later Upper Palaeolithic cultures, e.g., Gravetian or Epigravettian, were not found. Palaeolithic sites were also not found in Turkish Thrace west of Buyuk Cekmece, and a palaoenvironmental barrier, perhaps a channel connecting the Marmara and Black Seas, may have existed before the Bosphorus was opened in the Holocene. A difference int he distribution of Lower-Middle Palaeolithic sites and EUP sites was also noted. EUP sites are clustered on the Black Sea coast while earlier sites are found in the interior and on the shores of the Sea of Marmara. This change in settlement pattern may support a hypothesis of cultural change between the Middle and Upper Palaeolithic and perhaps the replacement hypothesis for the peopling of Europe by early modern humans.