Disadvantages of lime treatment include a reduction in compacted dry unit weight and rather slow strength gain. After a short literature review, engineering property changes obtained from salt, lime, and salt-lime treatment of two cohesive soils are summarized in support of two hypotheses: (1) Lime-clay reactions occur in two distinct states, modification for plasticity reduction and stabilization for strength gain, and (2) sodium chloride used as a chemical admixture in conjunction with lime improves compaction behavior and accelerates and enhances clay-lime reactions at both modification and stabilization lime contents. Data are presented to show that little alteration of clay mineral structure and new mineral formation occur during lime modification but clay structure is altered and new minerals formed during lime stabilization. Sodium chloride alters mineralogy of treated clays and produces new mineral formation at both modification and stabilization lime contents.