Dietary carbohydrates range in molecular size from simple sugars to complex polymers with a degree of polymerization (DP) of up to 100,000 or more. Oligosaccharides are generally defined as carbohydrates from 2 to 20 monomeric units long. Oligosaccharides have been dietary staples since antiquity but have received much less attention than other carbohydrates such as simple sugars or dietary fiber. Recently, interest in oligosaccharides has increased not only because of properties that include sweetening ability and fat replacement, but also because of resistance to digestion in the upper gastrointestinal tract and fermentation in the large bowel. Thus, some oligosaccharides have functional effects similar to soluble dietary fiber such as enhancement of a healthy gastrointestinal tract, improvement of glucose control, and modulation of the metabolism of triglycerides. These oligosaccharides are the nondigestible oligosaccharides. These compounds are easily incorporated into processed foods and hold much promise as functional ingredients in nutraceutical products.