The focussed beam reflectance monitoring (FBRM) instrument developed by Lasentec is a 'powerful' tool used as an 'in-situ' particle monitoring technique for in-line real-time measurement of particle size. This technique was successfully used to monitor particulate attrition and breakage of an organic fine chemical in a turbulently agitated suspension. The great advantage of using the FBRM technique is that the change in the crystal size distribution (CSD) for different particle size classes (fine, intermediate and coarse) can be monitored as a function of time. The attrition rates can be calculated to produce a model for the disruption kernel for the organic compound. The shift in the CSD that was observed with an increase in the specific power input was found to be largely due to micro-attrition effects rather than particle breakage (splitting). (c) 2005 Elsevier B.V. All rights reserved.