The cone penetrometer test (CPT) is an important tool for use in geotechnical and environmental site characterization for the transportation sector. Its role as both a primary investigation technique and as a component in an overall exploration strategy are explained. The types of sensors currently used with the CPT are discussed. Among the most promising new CPT technologies are a soil moisture probe and a fluorescence detection system. Laboratory and field results using a soil moisture probe jointly developed by Ohio University and Applied Research Associates for use with the CPT are presented. Also, application of the fuel fluorescence detector (FFD) for locating hydrocarbon contamination is presented, and typical data obtained with the FFD are illustrated and discussed.