The result of these studies was that important quality parameters for the industrial manufacturing of the lyophilisate Prednisolut® 100 mg N could be ascertained: Differential scanning calorimetry method showed that prednisolone-21-hydrogen succinate is fully converted to its sodium salt. A glass transition occurs; X-ray diffraction studies proved that the lyophilisate has an amorphous microstructure. Using model formulations of Prednisolut® 100 mg N as examples, it was shown that both the residual moisture and the buffer used have an influence on the glass transition temperature of the lyophilisate. By a simulation of the freeze-drying in the Environmental Scanning Electron Microscope (ESEM), it was possible to picture the forming of the lyophilisate's porous structure. The interfacial surface structure formed during the freezing serves as a structural framework. Studies of aqueous solutions of Prednisolut® 100 mg N by Tensiometry, Capillary Electrophoresis and Dynamic Light Scattering proved that the formation of micelles out of the active drug substances is a prerequisite for their pharmaceutical-technological stability. The analyses made by Capillary Electrophoresis confirmed the Critical Micellization Concentration (CMC) values determined by Tensiometry. The micelle diameters are in the order of magnitude observed for the micelles formed by simple bile salts. The size of the micelles as a function of the concentration of the active drug substance remains approximately constant. As the water content decreases, the micelle density increases. Hence, the freezing process can be better understood that occurs when aqueous preparations are lyophilized during the manufacturing of Prednisolut® 100 mg N.