This Special Issue of the Int. J. Geomech. on soft clay engineering and soft clay improvement is a result of discussion among various colleagues during the Geo-2000 Conference in Melbourne, where the need for a Special Issue on soft clay engineering and improvement was raised. The papers contributed to this Special Issue are selected to reflect the latest developments relating to soft clay engineering and improvement, and address research and applications in many places around the world ~e.g., Australia, Finland, The Netherlands, Norway, Singapore, United Kingdom, and the United States!. This Special Issue covers a variety of aspects for soft clay engineering and improvement, including constitutive modeling, numerical and analytical methods, design parameters, field and laboratory testing, and case studies. The issue begins with an invited introduction by Chandra S. Desai, of the University of Arizona, titled “Constitutive Modeling for Geologic Materials: Significance and Directions.” It draws our attention to the importance of developing appropriate constitutive models for solving geotechnical problems. Prof. Desai presents a brief but comprehensive overview of the available constitutive models for soft soils, and describes briefly the recently developed unified model based on the disturbed state concept ~DSC!. In their study on “The Effect of Anisotropy and Destructuration on the Behavior of Murro Test Embankment,” M. Karstunen, H. Krenn, and S. Wheeler of University of Glasgow, M. Koskinen ~Helsinki University of Technology!, and R. Zentar ~Ecole des Mines de Douai! investigate, further, the importance of adopting proper constitutive models for simulating the behavior of soft soils. The paper demonstrates the influence of anisotropy and destructuration on the behavior of soft clay soils using the finiteelement analysis and three different constitutive models that have been recently developed to account for anisotropy and destructuration. The study also compares the results of numerical analyses with field observations for a test embankment constructed at Murro, Finland. “Uplift Phenomenon: Model, Validation, and Design,” by M. Van, A. Koelewijn, and F. Barends, of Delft University of Technology, proposes a new analytical stability design method for uplift-induced slope failure as a result of high water pressures in sand layers below soft topsoil layers. The study verifies the results of the new proposed design method by conducting appropriate geocentrifuge testing, a full-scale field test, and finite-element numerical modeling. Furthermore, the authors compare the results of the new design method with four existing methods for ten Dutch polder dikes in The Netherlands. The new method is now accepted in the Dutch national guidelines for dike design. The study on “Loads on Braced Excavations in Soft Clay,” by K. Karlsrud and L. Andresen of Norwegian Geotechnical Insti-