This work concerns the effect of aqueous ammonia pretreatment at four temperatures and at 10, 20 or 30wt.% ammonia. After 1h, more than 65% delignification is achieved at 150 or 180<SUP>o</SUP>C for high and for low concentrations of ammonia. When the delignified miscanthus is enzymatically hydrolyzed for 96h using cellulases and beta-glucosidase, conversion of the recovered solid to glucose is 53.4% and to xylose 70.0%. Additional glucose and xylose can be obtained from the ammonia-containing aqueous phase. Increased ammonia concentration leads to better conversion. Fourier-transform infrared and Two-dimensional <SUP>13</SUP>C-<SUP>1</SUP>H Heteronuclear Single Quantum Coherence (HSQC) Nuclear Magnetic Resonance spectroscopy provide data for the composition of the pretreated miscanthus and for that of the liquid extract. These spectra indicate that pretreatment with ammonia leads to de-acetylation of the xylan-backbone. The β-O-4' linked aryl ether remains the most abundant linkage in the pretreated miscanthus.