Sintering of Fe-W-Mo systems under a dynamic atmosphere of argon has been studied by different experimental techniques, including dilatometric trials, X-ray diffraction, optical microscopy and electron probe microanalysis. It has been found that sintering at 1300 degrees C for only 10 min allows compacts to be obtained with a relative density close to 80%. The results also show an improvement in the final density by molybdenum addition. On the other hand, the structure of the sintered samples was, mainly, constituted of a soft matrix of (Fe-M)(alpha), solid solutions (similar to 300 H-v) in which hard intermetallic compounds (similar to 1200 H-v) are dispersed. Furthermore, perturbing expansions have been observed during the sintering cycle. The fi rst expansion occurred at about 620 degrees C as a consequence of a Kirkendall effect. The second one arose at about 890 degrees C in relation to Fe7M6 (where M is tungsten or molybdenum) formation. The latter expansion occurred at about 1200 degrees C as a consequence of an increase in tungsten diffusion from indiffused areas to (Fe-M)(a) solid solutions and intermetallic compounds.