Cesium salts of 12-tungstophosphoric acid, Cs(x)H(3-x)PW(12)O(40) (Cs(x)PW), in the bulk form or supported on medium-pore MCM-41 (3.7 nm) or large-pore (9.6 nm) micelle-templated silicas are active solid acid catalysts for the cyclodehydration of xylose into furfural, in a toluene/water solvent system (T/W) or in dimethyl sulfoxide (DMSO). The catalytic results are comparable to those obtained using sulfuric acid, under similar reaction conditions. The initial activities increase in the order H(3)PW(12)O(40)<Cs(2.0)PW<Cs(2.5)PW<silica-supported CsPW catalysts (15, 34wt% PW). Higher HPA loadings, larger pore diameter of the parent silica support, and higher reaction temperatures lead to higher furfural yields. The stability and reusability of the MCM-41-supported CsPW is higher in DMSO than in T/W.