The 66 papers presented in ""Geotechnical Special Publication No. 122"" contain the Proceedings of the Ninth Multidisciplinary Conference on Sinkholes and the Engineering and Environmental Impacts of Karst, co-sponsored by the Geo-Institute, National Groundwater Association, and P.E. LaMoreaux and Associates, Inc. Karst terrain presents unique engineering and environmental problems. The top rock is highly irregular and the rock itself is often riddled with voids, creating unreliable foundation conditions. Precipitation drains down the rock rather than running off over the surface and erodes the surficial sediments downward, causing sinkhole collapse and ground settlement. Groundwater moves rapidly through dissolved drainage channels in the rock resulting in a turbulent flow, which allows pollutants to be transported great distances very quickly. Traditional groundwater quality monitoring systems as required by many regulations are inapplicable in karst terrains and may fail to detect contaminants. The unique set of problems requires new and innovative techniques developed by engineers and scientists from all over North America, Europe, Asia, and the Middle East. They have contributed their expertise to this conference: the world's leading forum on new developments and cutting-edge technologies for avoiding and solving these problems in karst. The conference was held September 6 through 10, 2003, in Huntsville, Alabama, USA.