Dictyostelium discoideum was immobilized by cultivation on inorganic porous matrices consisting of broken pumice or a ceramic catalyst carrier (CeramTec) to produce human soluble Fas ligand (hFasL). These supports were actively colonized by D. discoideum reaching cell (number) densities 10–20 times higher locally than those observed in suspension culture under similar conditions. In repeated batch or continuous operation, hFasL productivities of up to 15–25 μg h−1 l−1 pore volume were attained. The immobilized cell densities and hFasL productivities could be kept constant for a long period of time by repeated renewal or continuous feeding of complex or synthetic medium.