Kinetic measurements suggest that neighbouring acetamido-group participation occurs in the spontaneous hydrolysis and methanolysis of o-carboxyphenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside and in the spontaneous hydrolysis of 2,4-dinitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside and 2-acetamido-2-deoxy-beta-D-glycopyranosyl fluoride. The methanolyses of these compounds proceed with predominant retention of configuration which is also consistent with neighbouring acetamido-group participation. The oxazoline intermediate which would arise from such a process was detected during methanolysis of 2-acetamido-2-deoxy-beta-D-glucopyranosyl fluoride in the presence of bases by n.m.r., i.r., and u.v. spectroscopy. Attempts to isolate the oxazoline were unsuccessful.