Porous ceramics were fabricated by firing ceramic-polymer composites prepared by casting dispersions containing cellulose acetate, water and colloidal ceramic particles (alumina and silica). Composite microstructures were determined by polymer phase Separation. Polymer adsorption on the ceramic particles was necessary for the formation of controlled porosity in the composite and fired ceramic. Cellulose acetate adsorbed on alumina, but not silica particles. The micro structure of alumina-cellulose acetate composites was characterized by unagglomerated alumina particles in a polymer matrix; relatively large pores (pore diameter similar to 15 mu m) formed when the alumina concentration was low (< 50 vol % relative to the polymer in the dried composite), and smaller pores (pore diameter similar to 2 mu m) developed at higher alumina contents. By contrast, silica-cellulose acetate composites contained agglomerated silica particles and a large pore structure invariant to silica content. Firing of alumina-cellulose acetate composites with ceramic contents greater than 40 vol. % resulted in crack-free porous ceramics with pore structures comparable to the original composites.