Material characterization plays a crucial role by means of equipments efficiency and overall circuit performance. Material properties such as grindability, breakage, crushability, mineralogy can easily be determined by laboratory studies. These parameters are required for modeling and simulation works. Breakage behaviour of material is important for size reduction equipments and it is defined by breakage distribution function. Commonly, single particle breakage method is used to determine breakage behaviour of materials which assumes that breakage is not size dependent. As new surfaces formed material behaviour changes so particle size effect should also be introduced into the grinding model structure. Determination of fine particle breakage becomes important. This will make models more reliable. With this aim a bed breakage method was developed for determination of fine particle breakage. In this study new breakage model is presented and effects of different breakage distribution functions on breakage rate and discharge function is investigated. The bed breakage test results are compared with single size drop-weight test results in the aspect of modeling. It was observed that, the breakage rate and discharge function variation by size indicates a characteristic change at fine size ranges compared to regular curve. (C) 2010 Elsevier Ltd. All rights reserved.