Traditionally, unconfined compression tests are carried out on lime and cement treated soft clays with parametric variation of the additive content and curing time. These studies were most valuable in having a good understanding on the pseudo modulus and strength of the treated clays. In this paper, some pioneering works carried out under triaxial undrained, drained and isotropic and anisotropic consolidation conditions are presented and discussed within the frame work of using deviator stress, mean normal stress and voids ratio (or water content); the so-called state boundary surface and the associated stress-strain behaviour. The results clearly illustrate the effect of additive content and the curing time in the development of pore pressure and shear strain under undrained condition and the volumetric strain and shear strain during the drained case. The dilatancy ratio seems to be similar to the untreated behaviour while the development of pore pressure is suppressed and also the volumetric strain under the drained condition. The treated strength lies between those of the critical state and the tensile fracture envelope. Strength degradation beyond the peak is also illustrated with continuous shear.