Extensive sampling campaign was performed around the cement grinding circuit of a cement plant in Turkey, for different production types of cement, as CEM I 42.5, CEM II 32.5/42.5/52.5, for the modelling and simulation purposes. During the sampling surveys; samples were collected from around the circuit for the steady state condition of the operation and, following a crash stop, from inside the mill. The size distributions of the samples were determined down to 2 pm by the combination of sieving and laser sizing methods. By using the size distributions around the circuit and control room data mass balance studies were performed. Then equipments in the circuit; ball mill, air-classifier and filter, were modelled individually by using the appropriate model structures. After modelling the circuit, simulation studies were performed for capacity improvement, mainly by the ball size optimization. By implementing the proposed optimization, the capacity of the circuit was increased up to 12.7-20.5% for different production types, hence; the overall specific energy consumption of the circuit was reduced, as predicted in simulation studies. (C) 2010 Elsevier Ltd. All rights reserved.