Compression-permeability cells are utilized for measurement of porosity and permeability of compressible cakes. Shortcomings of the cells have tended to be minimized in the literature. Data are presented which show that the stress distribution in typical C-P cells is highly nonuniform because of wall friction. For compressible materials, the porosity and permeability would also be nonuniform. Use of large L/D ratios and minimizing wall friction are essential to proper use of C-P cells.