A series of isotropically consolidated undrained triaxial tests has been performed on an artificially cemented marine clay using lime as an additive. This procedure is helpful to simulate the behavior of naturally cemented marine clays often found in many coastal and offshore areas. By comparing the undrained shear behavior of artificially cemented samples with the available data on the naturally cemented marine clays, the effect of cementation on the mechanical properties of clays is evaluated. The results show that cemented soils display smaller strain at failure, higher strength, a gradual reduction in shearing resistance with increase in consolidation pressure, and a nonlinear failure envelope in effective stresses. Within the degree of cementation considered in this study, the cementation is shown to have little affect on the generation of pore pressure. The article discusses the phenomenon of a “phase transformation”; and its relation to the existence of bisegmental stress-strain behavior, typical of cemented clay. The overall results demonstrate that the effect of natural cementation can be conveniently studied in the laboratory using artificially induced cementation in the soil. © 1998 Taylor and Francis Group, LLC.