Authors had developed a tube rheometer to supplement a Netzsch MiniCer (Netzsch GmbH, Germany) stirred media mill in order to monitor online the theological characteristics of the suspension and therefore the result of grinding during the process. It was demofistrated that the above measuring system was working appropriately based on the preliminary tests. The product related stress model was applied for the evaluation of the grinding results. It was found that the rheological behaviour of the suspension strongly affects the grinding result, i.e. specific surface area, median particle size as well as specific grinding energy. The tested model material limestone water suspension behaved Newtonian initially, then after a given grinding time their properties had changed to Bingham plastic, occurred more or less at the same produced specific surface area at about 10 m(2)/g for each tested concentration. A separate off-line validation test with a rotational rheometer had been also implemented to verify the Bingham approximation; correlation was very good. (C) 2016 Elsevier B.V. All rights reserved.