A description of the use of a liquid displacement (modified bubble-point) method to characterize tubular membrane microfilters in terms of pore sizes and pore-size distributions is given. Following a theoretical analysis the method, some comments about pore-size distribution of tubular filters and experimental results for different ceramic microfilters are presented. The characterization studies reported in this paper are applicable to other ceramic membranes, and they represent a significant step in an understanding of ceramic membranes in various applications.