Morphologies of ceramic hollow fibre membranes prepared from suspensions of Al2O3, NMP (N-methyl-2-pyrrolidone) and polyethersulfone (PESf) using a dry-wet spinning/sintering process have been studied experimentally The results indicate that two types of membrane morphologies, i.e. finger-like and sponge-like structures can be expected. It is believed that finger-like void formation in asymmetric ceramic membranes is initiated by hydrodynamically unstable viscous fingering developed when a less viscous fluid (non-solvent) is in contact with a higher viscosity fluid (ceramic suspension containing invertible polymer binder). Finger-like void growth occurs only below a critical suspension viscosity, above which a sponge-like structure is observed over the entire hollow fibre cross-section. The effects of the air-gap, viscosity and non-solvent concentration on fibre morphology have been studied and it has been determined that viscosity is the dominating factor for ceramic systems. Crown (c) 2008 Published by Elsevier B.V. All rights reserved.