AbstractIn a literature review is stated that the attempts to lessen the divergence between theory and practice of the determination of particle size distribution have not yet been successful. One of the significant causes of the observed deviations are abrasion and breakage. For this an effective growth rate re = rc + rs is postulated (rc – mean linear growth rate, rs – mean linear rate of size change by abrasion and breakage). Two models for the relation between these quantities are presented. – The dependence of attrition rate on particle size, especially in a CMSMPR crystallizer is discussed.