Dilute aqueous solutions of 1-(1-propylsulfonic)-3-methylimidazolium chloride and p-toluenesulfonic acid are shown to be better catalysts than aqueous sulfuric acid of the same H+ ion concentration for the degradation of cellulose at moderate temperatures and pressures. For example, Sigmacell cellulose (DP ≈ 450) in aqueous solutions of 1-(1-propylsulfonic)- 3-methylimidazolium chloride, p-toluenesulfonic acid, and sulfuric acid of the same acid strength (0.0321 mol H+ ion/L) produced total reducing sugar (TRS) yields of 28.5%, 32.6%, and 22.0%, respectively, after heating at 170 °C for 3.0 h. In the same set of experiments, glucose yields of 22.2%, 21.0%, and 16.2% were attained in 1-(1-propylsulfonic)-3-methylimidazolium chloride, p-toluenesulfonic acid, and sulfuric acid mediums, respectively. © 2011 American Chemical Society.