Abstract: The rheological properties of benzene and heptane solutions of cobalt monooleate soap have been investigated. The solution viscosity increased up to a steady equi- librium value with aging time. A remarkable non-Newtonian behavior was observed even with dilute soap solutions. The thickening ability of cobalt monosoap in non- polar media may be ascribed to the formation of polymer chains through the coo- rdination bonding between soap molecules. The high solution viscosity decreased to the same level as the solvent alone in the presence of small amounts of additives containing groups with strong coordinating ability with cobalt atom.