Having proved its success in energy efficiency, the High Pressure Grinding Rolls became widespread all over the world in many plants. The first application of the HPGR was in 1985 in a cement plant, mainly for capacity improvement purpose. Then various circuit configurations were derived to achieve reduction in overall specific energy consumption by transferring more of the grinding required to the HPGR. By mid 1990s, HPGR installations have been used in minerals industry. The HPGR was introduced to minerals industry as a replacement for tertiary crushers, SAG mills and rod mills. In some applications it appears as a pebble crusher in AG milling. HPGR has attracted the attention of many researchers for around two decades, resulting in various modeling approaches for throughput or size reduction of the equipment. This paper will discuss the method of applying population balance model to size reduction of HPGR. Data collected from both cement and minerals industry was used for this study. The breakage rate was defined as a function of the operating pressure and the material characteristics. The material characteristics were determined by compressed bed breakage tests. The relationships between the operating parameters and the model variables lead to predicting the product size distributions of the HPGRs for the given operating conditions. (C) 2013 Elsevier Ltd. All rights reserved.