The action of levan sucrase of aerobacter levanicum on sucrose was investigated at different substrate concentrations. Furthermore the influence of certain acceptors (glucose and glycerol) on this reactions was studied with respect to variations of the rates of the three reactions (levan formation, inversion and oligosaccharide formation). The kinetic data give evidence that all subreactions proceed over the same enzyme substrate complex. It is assumed that the polymerisation reaction, building up the levan chains, follows an insertion mechanism. A reaction mechanism is proposed for the simple reaction. Equations for the rates of the three reactions are developed. In order to be able to perform these calculations it was assumed that the reaction of the complexes are rate determining in the overall reaction, and the Michaelis and acceptor equilibria are undisturbed during the reaction. The constants in the equations of these reaction rates (Michaelis constant, acceptor constant and the maximum rates of the three reactions) have been determined from experimental data. It is shown that the equations are in good agreement with the experimental data. If acceptors are added to the reaction, the reaction mechanism has to be extended. The equations for the reaction rates and the additional acceptor constants were determined in the same manner as above. Again, good agreement with the experimental data was obtained. Adding glycerol to the reaction a new product was detected and identified as dioxypropylfructoside. The rate equation of its formation was evaluated from the reaction mechanism.