Previous work (Proceedings of World Congress on Particle Technology, Sydney 2002, 629-636.) has shown that granule breakage occurs during fluidised bed melt granulation (FBMG) and should not be neglected when it comes to addressing granulation kinetics. In the current work, we have developed and verified tracer experiments in FBMG, in an attempt to decouple the influence of granule size and age on breakage kinetics. The tracer data during granulation shows that granule breakage is occurring at a much slower rate than aggregation, while the breakage-only tracer experiments reveal the breakage selection rate to be independent of size at an approximate value of -0.01 s(-1). The observations allow us to deduce that the aggregation rate for smaller granules is actually faster than larger ones during granulation. (c) 2005 Elsevier Ltd. All rights reserved.