Porous membranes having nanometer and smaller pores challenge existing characterization methods. An easy, fast and inexpensive method to determine the maximum pore size and the pore size distribution is offered by the bubble point technique. Several methods based on similar principles have been presented in the literature. Here the original bubble point test and a liquid-liquid variation are considered. Two types of ceramic membranes with very different morphologies have been characterized with these methods in our labs. Results obtained for Anodisc(R) flat disc membranes with straight, non-intersecting pores using binary and ternary probing liquid systems are in very good agreement with each other and the manufacturers characteristics. On the ether hand, analysis of tubular gamma-alumina membranes, i.e., Membralox(R), resulted in two phase flow within the pores, and hence information about the pore size distribution could not be extracted from these tests.