Supercritical MeOH and MeOH-H2O (90/10) mixtures were used as reaction media for one-pot dissolution-conversion of microcrystalline cellulose. In the absence of catalyst, the cellulose dissolution was almost complete under supercritical conditions (300 degrees C/10 MPa/1 min) but relative low amounts of value-added chemicals were obtained. Addition of solid acid catalysts such as CsxH3-xPW12O40 or sulfated zirconia led in the same conditions to formation of valuable methyl-levulinate in remarkable yields close to 20%.