A range of mesoporous vanadosilicate molecular sieves with the MCM-41 structure and the atomic ratio Si/V=10–160 have been synthesized using vanadyl sulfate as the source of vanadium. The products were characterized by XRD and 51 V and 29 Si MAS NMR spectroscopy. The increase of the unit-cell parameter (monitored by XRD) and the decrease of the Q 3 /Q 4 ratio (determined from the 29 Si spectra) with increasing vanadium content indicate the incorporation of vanadium into the MCM-41 structure. In as-synthesized [Si,V]-MCM-41, vanadium is in an octahedral environment and is located mainly on the surface of the channels. The amount of octahedral vanadium decreases and tetrahedral V is increasingly created as the calcination temperature increases.