The wide variety of naturally occurring polysaccharides that are composed of different monosaccharides linked by glycosidic bonds of varying acid lability precludes an overall adequate procedure for their complete acid hydrolysis. Depending on the monosaccharide composition of the individual polysaccharide, the ring form of the component sugars, and configuration of the glycosidic bonds, reasonably satisfactory acid hydrolytic conditions may be devised for several general types of polysaccharides. These methods are based on the following considerations: furanoside linkages are much more labile than pyranoside linkages, alpha glycosidic bonds are usually more labile than beta, and other considerations described in the article. The polysaccharides dealt with are arbitrarily divided into classifications for purposes of describing acid hydrolytic methods as most suitable for each of them. With certain polysaccharides it may be advantageous to apply the described methods in a sequentially graded hydrolysis.