DMOD2000 is a one-dimensional nonlinear effective-stress site response analysis computer program, i.e., a computer program that allows for the time-dependent generation of porewater pressure and accounts for its effects on soil stiffness and strength over the duration of an earthquake. The nonlinear response of the soil is represented by a backbone curve with inelastic response governed by unloading-reloading rules postulated by Masing and Pyke. Porewater pressure generation is controlled by semi-empirical models developed by Dobry and Vucetic (for sand) and Matasovic and Vucetic (for clay), with a computed porewater pressure used to degrade the backbone curve in a way that represents the softening and weakening of soils expected at lower effective confining pressures. Our long-term goals include continuous update of our programs D-MOD2000, SHAKE2000 and RspMatchEDT; and sharing our experience and knowledge with the engineering and academic communities.