ABSTRACT: İkitelli Organized Industrial Region is under development at the north of Küçükçekmece lake in the westof Istanbul, It is the second largest investment project in Turkey in recent years after GAP (Southeastern Anatolian Project) and based on the 1991 data, it comprises about 50 light indusüial plant cooperatives with approximately 17 000members. The consuiiction activities at this Industrial Region started prior to the suitability for development studies were earned out. In this paper, the findigs of the geological and geotechnical investigations over an area of approximately20 km2 at ikitelli Organised Industrial Region and the vicinity are presented. The geological base of the investigatedarea consists of alternating layers of siltstone-sandstone and shales of Carboniferous Age, which is known as TrakyaFormation, This formation which is generally called graywacke, is observed to be in a state of solid rock, intermediaterock and weathered rock from base to top, and this observation is verified with laboratory determined mechanical properties. In the region, Eocene aged Kırklareli and Menekşedere formations overlay discordantly the Trakya formation.The Kırklareli formation is represented by harddense limestones, and at the upper levels grades to Menekşedere formation which is represented with sandy clayey limestones interbedded with marl and both formations are observed to formthe steep slopes of the valleys due to their high strength characteristics. These formation are overlaid by Miocene agedÇukurçeşme formation consisting of sands and gravels of transgressive character, Çukurçeşme Formation possessescharacteristics of dense sand-gravel with a weak cohesiveness due to the presence of clay inclusions and bands. AboveÇukurçeşme formation, highly plastic clays of Güngören formation with occasional clayey silty sand lenses irBHCOuntered. This formation which is observed to outcrop in the areas with small slope angles tend to become unstable in excava tion slopes and leads ta earth movements, It is overlain by clayey porous limestones of Bakırköy foımation* All thesegeological units are covered with alluvial deposits. In this investigation, the 1/5000 and 1/1000 scaled geological and engineering geological maps are prepared for the İkitelli Industrial Region and the vicinity, on which all the outcroppingrock-soil formations are identified» and the physicomechanical properties of the geological units encountered are determined with laboratory tests. The thickness» structural location, fault-contact-groundwater relationships, constitutive andtexture characteristics, and strength properties are evaluated in the view of stability and suitability for constructional development considerations. Inclination maps are also prepared and the results of all the field and laboratory geotechnicalinvestigations are utilized to prepare land use suitability maps for the whole region,