The MRittmann Software allows us to calculate the Rittmann Norm for igneous rocks, especially for volcanic ones. The bulk composition of a rock sample as input data is compiled and analyzed by MRittmann to estimate the mineral components of the sample in volume percentage. Because of the advances in principles of Rittmann’s method, an useful feature of the MRittmann Software is that its output data is realistic for deep studies on igneous petrology. MRittman is implemented on a 486-class PC using Windows 95 and a 586-class PC running Windows 9x, NT 4.0. It was developed in January 2001, and MRittmann 1,0 was released in May 2001. The program is a copyrighted work with all copyrights vested in Faculty of Geology, Hanoi University of Natural Sciences, ViÖt Nam National University.