New markets for membranes have resulted from recent developments in biotechnology and growing interest in environmental science. These applications make increased demands on the membranes, which in many cases cannot be met by polymer membranes. The preparation and characterization of a new ultrafiltration membrane composed of MgAl2O4 is described, which exhibits improved chemical and thermal stability with respect to phase transition, pore size, and particle growth compared to other inorganic ultrafiltration membranes.