The increasing demand for "finer cement" products, and the need for reduction in energy consumption and green house gas emissions, necessitate the optimization of grinding circuits. Opportunities exist at cement plants to improve energy efficiency while maintaining or enhancing productivity. Several technologies and measures exist that can reduce the energy consumption of the various process stages of cement production including raw and finish milling. This paper presents one of these technologies, which is pregrinding with Barmac B-Series Vertical Shaft Impactors (VSI) in raw and finish milling. Recent pilot plant studies conducted at Metso Minerals show that significant clinker size reduction occurs in Barmac VSI crushers, which can increase the cement mill throughput and decrease the energy consumption in finish milling. In addition, a number of grinding simulations using JKSimMet software conducted to date have been presented. The simulation results show that pregrinding increases mill throughput by 14 to 26%.