One of the most important technological developments for characterization of unconsolidated sediments in the past 20 years is the direct-push method for accessing and probing the subsurface. The cone penetrometer and related direct-push technologies, such as the Geoprobe, have increasingly been used for geologic and chemical characterization at sites throughout the United States and abroad. In addition to its standard suite of sensors (i.e., tip pressure, sleeve friction, and capillary pressure) to determine soil type, the cone penetrometer has been used with innovative sensors and samplers to perform contaminated site assessments and has also been used to install wells, sampling points, and geophysical tools and arrays. By integrating geologic information from the standard cone penetrometer sensor with the depth-discrete chemical and physical information obtained from innovative cone penetrometer-based samplers and sensors, an accurate, rapid, and cost-effective characterization can be accomplished. Cone penetrometer tests provide quality, high-resolution data. The tests are minimally invasive, rapid, and produce a minimum of investigation-derived waste. These attributes are critical to investigative and cleanup operations at large hazardous waste sites with heterogeneous sediments.