Seismic piezocone penetration tests (SCPTu) with dissipation phases are particularly useful for geotechnical site characterization as they provide four independent readings with depth from a single sounding, as well as time-rate information. Methods of evaluating the degree of preconsolidation, stress state, strength, stiffness, and permeability characteristics of sands and clays are reviewed with example applications. For clays, a combined cavity expansion and critical-state model has proven useful. For sands, chamber test results have guided the interpretation of parameters.