Hollow fibers used in membrane filtration units submerged into the biological stage into the biological stage of a municipal wastewater treatment plant, so-called membrane bioreactors (MBR), are investigated in terms of pore structure, membrane morphology, and membrane materials characteristics. In order to reduce production costs and to optimise the filtration performance, membrane samples manufactured under different production conditions are analyzed by means of pure water filtration tests, molecular weight cut-off (MWCO) measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). These analytical tools are evaluated regarding their significance to predict the impact of production conditions on membrane properties and by that on the susceptibility to fouling. In this paper, initial results of membrane characterisation are discussed and the next steps to develop a membrane characterization protocol are outlined.