The Thesis title is : "Development of dense high performance low alloy PM steels by liquid phase sintering”. The master alloy concept as a mean for obtaining high density low alloyed PM steels was revisited. In a first instance, several master alloys previously reported in the literature, were reproduced in order to carry out experimental sintering trials with the aim of understanding the behaviour of these master alloys, mixed in predetermined proportions, with a selection of Fe-based powders. As a secondary objective the accuracy of theoretical predictions based on ThermoCalc calculations was compared against the reported experimental data. A conjunction of this information with additional experiments tending to determine the diffusion paths and rates of a diversity of elements in multicomponent Fe-based systems was used for identifying adequate alloy additions supported by a computer aided alloy design approach. On these bases, several mater alloys have been specifically designed, under metallurgic and thermodinamic criterion, to provide the formation of wetting liquid phases at low temperature and also, attractive mechanical properties of the steels. The as-sintered density and properties of the alloys is determined by the amount and type of master alloy used, total carbon content, the sintering temperature and time. The performance of the master alloys during sintering is shown for several commercially available Fe-based powders. The microstructural development of the steels is determined, both, by the chemical composition of the Fe-based powder and the chemical reactions taking place between the Fe and the master alloy particles during high temperature sintering. The influence of alloying and the sintering conditions on the final microstructure, density and mechanical properties is also discussed. The thesis has been given the Schunk Materials Prize 2005 because the work in the field of sintered metal technology has distinguished itself by its scientific significance.