Experimental results obtained during the batch cooling solution crystallization of a fine organic compound in aqueous ethanol solvent are presented. The process monitoring was ensured through in-line, in situ ATR FTIR spectroscopy, providing continuous solute concentration estimates. Off-line image analysis was also performed to yield discrete-time measurements of the 2D-crystal size distribution (CSD) of the platelet-like particles. The decisive effect of secondary nucleation on both the course of supersaturation and CSD was highlighted through the qualitative analysis of selected batch runs, particular attention being focused on the seeds size and weight. At least two nucleation mechanisms allow explaining the experimental results: the introduction of seeds causes a significant burst of surface nucleation and the continuation of the cooling process, through the generation of continuous supersaturation, allows activated secondary nucleation to take place. (c) 2006 Elsevier Ltd. All rights reserved.