The tensile strength and the resistance to densification of fine lactose powder coated with increasing amounts of a series of fatty acids were examined over a range of temperatures from —10° to +53 °C. At a constant packing fraction and selected homologous temperatures both the tensile strength and the resistance to densification initially increase then decrease to minima and finally increase again as the amount of fatty acid present is increased. These results are explained in terms of the successive lubricating and binding action of the fatty acids.