A catalytic system constituted of a simple mixture of alpha-Sb2O4 and MoO3 shows very high performances in the selective oxidation of methanol to formaldehyde. Selectivities are equal or surpassing those observed in commercial iron-molybdate catalysts. It is suggested that a remote control mechanism via spill-over could explain satisfactorily the catalytic performances in this biphasic catalyst. MoO3 contains catalytic sites for the oxidation of methanol. The role of alpha-Sb2O4 could be principally to increase the rate of reoxidation of MoO3, avoiding the formation of too reduced structures and maximising the number of active selective sites on it. The potentialities of this catalytic system in industrial applications are discussed.