On August 17, 1999, the Izmit (Kocaeli) Earthquake tore through Kocaeli, Turkey, resulting in over 15,000 deaths and 27,000 injuries; 200,000 people were left homeless. The electric power system, nearly destroyed, sustained over US$70 million in damage. Another earthquake, November 12, to the east of Izmit at Duzce, added to the lifeline systems damage, impacting the communications system, water and wastewater system, ports, railway, road, and bridges. The Earthquake Investigation Committee of the Technical Council of Lifeline Earthquake Engineering (TCLEE), American Society of Civil Engineers (ASCE), established to initiate, organize, train for, coordinate, and evaluate the performance of lifelines following earthquakes, sent volunteers to Turkey to gather data to provide information for practitioners to improve the performance of the lifeline systems. Their findings are contained in this report. The topics include: seismology, geology, and geotechnical issues; electric power; airports; telecommunications; water and wastewater; transportation (highways and bridges); liquid fuel facilities; railway; ports; hospitals; social impacts; and emergency response and recovery.