Abstract: An expansion theory of cylindrical cavities in strain-softening materials with different moduli in tension and compression is presented. For geotechnical materials, two controlling parameters α and β are introduced to take into account the different moduli and strain-softening properties. By means of different modulus elasticity and stress-softening model, general solutions calculating Tresca and Mohr-Coulomb materials'stress and displacement fields of expansion of cylindrical cavities are derived. For expansion of cylindrical cavities, the ultimate expansion pressure, stress and displacement fields and development of plastic zone are found to vary with the different elastic moduli and strain-softening properties. If classical elastic theory is adopted and strain-softening properties are neglected, rather large errors may result.