Levulinates (methyl levulinate and levulinic acid) were produced from cellulose and eucalyptus wood chips in water and/or methanol solution under acid catalysis. In water, only levulinic acid was formed, and its yield was 4954 mol % of the glucan in biomass or about half of the glucan was wasted forming byproducts including insoluble humins. In a 90 vol % methanol solution, methyl levulinate was the main product, and the yield of levulinates reached 66 mol %. Protecting glucose from humins formation by quick conversion into methyl glucosides was found to be the key to a high yield of levulinates. Methanol had little effect on formation of humins and levulinates from 5-hydroxymethylfurfural. In addition to the main reactions with glucose, 5-hydroxymethylfurfural, and levulinic acid, methanol was also consumed in other reactions that caused a substantial loss of methanol and presented a technical challenge to using methanol in biomass refining.