Batchwise production of inulo-oligosaccharides from inulin was studied using soluble and immobilized endoinulinase under various initial inulin concentrations. The reaction behaviors and product composition of the inulo-oligosaccharides was significantly altered by the enzyme form and initial inulin concentration in the ranges of 50-150 g/l. Inulin was completely hydrolyzed to inulobiose and other higher oligofructosides with degrees of polymerization (DP) ranging from 2 to 7; several of the oligosaccharides produced were further hydrolyzed into small oligosaccharides, affecting the final oligosaccharide yield. For the same amounts of enzyme activity per gram of substrate, the initial reaction rates and final yields of inulo-oligosaccharides did not vary significantly with different inulin concentrations. In contrast, the product composition was considerably affected by the inulin concentration and enzyme form. In soluble form, the enzyme produced two major components, inulobiose and DP3 oligosaccharides, whereas when the enzyme was immobilized the inulobiose content was markedly higher doe to the diffusional restriction of sugars. The maximum yields of inulo-oligosaccharides using soluble and immobilized endoinulinase were 72 and 83%, respectively, reflecting the different contents of fructose and glucose.