This volume is the result of a workshop that was organised by Salam Al-Quntar and the editor of the present proceedings on June 11, 2014 during the 9th International Congress on the Archaeology of the Ancient Near East (ICAANE) in Basel, Switzerland. The workshop's aim was to stimulate colleagues studying the Neolithic and Chalcolithic periods in Mesopotamia to present papers investigating the development of human societies during the 6th - 4th millennia BC in Upper Mesopotamia. Of specific interest was the analysis of the "socio-economic complexity" phenomenon, seen as part of dynamics that cross the usual chronological boundaries (and thus not only as the result of typical 5th and 4th millennium BC processes). The ten contributions that compose the volume propose conclusions that go beyond such rigid subdivisions; moreover, many of them present the most recent data from key research projects currently ongoing in Upper Mesopotamia (north-eastern Syria, south-eastern Turkey and Iraqi Kurdistan). Therefore this volume offers an updated - and to some extent alternative - view of the crucial changes (such as different types of settlement pattern, variations in ceramic traditions, the use of new production technologies and emergence of early forms of urbanism) that characterised the region throughout the Neolithic and Chalcolithic periods.