Various methods to characterize the pore size and pore size distribution of hollow-fiber porous filtration membranes were reviewed. First, the microscopy observation method, which was the most direct method to characterize the membrane pore structure, was reviewed. Second, the thermoporometry method and a method based on water permeability were reviewed. The last method, which relates to solute or particle permeation performance, was reviewed in depth. Various transport models had been developed which could be used for the characterization, and the models and structure analysis by using the models were explained.