This proceedings of the Fifth U.S. Conference on Lifeline Earthquake Engineering, held in Seattle, Washington, on August 12-14, 1999, presents new developments and emerging practices that will advance the state of knowledge of lifeline earthquake engineering around the world. It includes over 100 papers covering a broad range of topics including: transportation systems; seismic hazards; pipelines; transportation projects; seismic risk analysis; water and wastewater; small group presentations; transportation criteria and analysis; case studies; port issues; social and economic issues; electric power; bridges, tunnels, and railroads; seismic risk applications; issues in implementation and investigation; and multi-hazard risk assessment. These papers provide a focus on lifeline topics of critical interest to the problems of infrastructure performance as we begin the new millennium.