The composition comprises a water dispersible colloidal siliceous material, such as a swelling clay, in intimate association with a low molecular weight water soluble high charge density organic polymer, such as a polyacrylic acid or a polyamine, the ionicity of the siliceous material being significantly modified by the charge on the polymer. The composition may be produced by reacting the siliceous material and the organic polymer in an aqueous phase system at a concentration, for example, of from 5 to 25 % by weight of the polymer on swelling clay solids. The composition is suitable for use as a retention/drainage agent in paper or paperboard production, preferably after the addition of a conventional high molecular weight flocculating agent.