The in6uence of the composition of a carburizing CH 4 +H 2 gas mixture on the process of reduction+carburization over WO 3 has been studied. Bulk tungsten carbide synthesis has been carried out from WO 3 in di4erent CH 4 +H 2 mixtures (CH 4 +H 2 ؍ 1/1+3/1; CH 4 +N 2 ؍ 1/1; pure CH 4 ) at atmospheric pressure by temperature-programmed reduction+carburization (TPRC). The composition of the reaction products has been monitored and quanti5ed by gas chromatography analysis (GCA) and the results have been compared to those obtained for a reference sample WC20 (CH 4 +H 2 ؍ 1/4). The solids have been characterized by elemental analysis, XRD, XPS, and BET surface area measurements. The overall process is complex. Considering 5rst the reduction, both H 2 and CH 4 act as oxides reducing agents and are converted respectively into H 2 O, CO, and to a less extent CO 2 . If the reduction steps follow the same sequence observed under pure H 2 , WO 3 PW 20 O 58 PWO 2 PW, with the strong di4erence that W metal is detected only at the surface to be rapidly carburized, the overall reduction process can be accomplished under CH 4 +H 2 mixtures at temperatures all the lower than P CH 4 /P H 2 increases. Prereduction of WO 3 into bulk WO 2 allows an easier reduction in practically pure CH 4 (95% (v/v) CH 4 +H 2 ) as reduction with CH 4 increases the rate of the WO 2 PW transformation. Studies of the carburization suggest that CH 4 decomposes on a metallic surface into C (or CH x ) species before bulk WO 2 reduction followed by surface carburization. Then carbon di4uses into the bulk of the solid to give 5rst -W 2 C whose formation occurs rapidly. -W 2 C transformation into WC is slower and seems to be very much in6uenced by the ratio P CH 4 /P H 2 which controls the rate of carbon deposit at the surface of the solid. The best surface area carbide of 27 m 2 .g ؊1 consisting of a core of -W 2 C covered with -WC has been obtained by using WO 2 as starting material.