Three decades after N-methylmorpholine N-oxide (NMMO) was first introduced as a solvent for direct cellulose dissolution, the usage of NMMO in the fiber-making industry has flourished throughout the world. This success attracts the attention of researchers working in lignocellulosic biomass fractionation to use NMMO as an agent for lignocellulosic pretreatment in biofuel production. The present chapter presents the current status of NMMO for the pretreatment of lignocellulosic biomass for further fermentation to biofuels.