A process for the production of cellulose, lignocellulosic sugars, lignosulfonate, and ethanol from lignocellulosic biomass. The process comprises steaming, pretreatment, chemical recovery, saccharification, and optionally fermentation. The pretreatment conditions use only sulfur dioxide and water, simultaneously resulting in high glucan conversion to glucose at low enzyme charges, high recovery of hemicellulose-derived monomeric sugars, high lignosulfonate yield, and the absence of lignin precipitates. High-yield production of ethanol through fermentation can be obtained using this process.