Methods of re-dispersing and de-agglomerating dewatered, partially dried and dried compositions of microfibrillated cellulose and compositions of microfibrillated cellulose and inorganic particulate material, into liquid compositions comprising same, by applying ultrasonic energy to such liquid compositions of dewatered, partially dried and dried compositions of microfibrillated cellulose, or compositions of microfibrillated cellulose and inorganic particulate material. Methods for preparing an aqueous suspension comprising microfibrillated cellulose and, optionally, inorganic particulate material, with enhanced viscosity and tensile strength properties, suitable for use in methods of making paper or coating paper, and to filled and coated papers made from such aqueous suspensions.