Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to result from uncontrolled occurrence of the mechanisms of nucleation, coalescence and layering. This study was undertaken to investigate the mechanism of pellet growth by layering. Several laboratory experiments were carried out to delineate the effect of feed moisture content and feed quantity. This paper presents an analysis of the experimental results and a simple model to describe the layering process. (C) 2002 Published by Elsevier Science B.V.