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The IGB has developed ceramic hollow fiber and capillary membranes of < 1 mm dia and 100-200/m wall thickness. They have a high membrane surface/volume ratio and thus a high packing density. The -Al2O3 hollow fiber carrier has pores of > 200 nm with narrow pore size distribution and can be used directly for microfiltration. For numerous other applications such as ultra-, nanofiltration and gas and vapor separation however additional membrane layers are used. The discussion covers various coating systems on a sol-gel basis such as spinel coatings and unmodified and modified Al2O3 coatings and their application to ceramic hollow fiber carriers. The application potential and the limits of the membrane coatings are considered. Besides use in ultrafiltration the coatings are suitable as intermdiate layers for additional separation layers such as nanofiltration layers, hydrogen selective metal layers, and selective polymer separation layers. Introducing selective polyme r separation layers into gas and vapor separation is an example. Because of the absolute solvent resistance of the substructure here in contrast to coated polymer membranes there are no application limitations. There are no limitations in the choice of coating solvent medium. Thus even polymers the covering of which needs the use of aggressive solvents, but that otherwise exhibit a high chemical or thermal resistance, is brought onto the ceramic carrier. By use of such resistant polymers the application range of the membrane is strongly broadened.