Twelve aluminized solid propellant formulations based on ammonium perchlorate (AP) were chosen to study the effect of various formulation parameters on the burning rate and the agglomerate sizes within a pressure range of 1 MPa to 12 MPa. The various propellant formulation parameters considered are the Al content, Al size, coarse AP size, fine AP size, and fine AP/binder ratio, and the type of curing agent. The choice of ranges of the fine AP size and fine AP/binder ratio is so as to produce plateau-burning rate trends, and the present work examines the alteration of such trends with addition of aluminium in lieu of the coarse AP. The results show that the trends in the burning rate and agglomerate size are monotonic with the coarse AP size, but not with the Al content and size. An inverse correlation exists between the burning rate and the agglomerate size, in general. The results are explained based on the interstitial size of the pocket between adjacent coarse particles in the propellant microstructure where the Al particles reside prior to burning, relative to their size and content, and on the prospect of the Al accumulates on the burning surface being ignited by the leading edge flames attached to the coarse AP particles. © 2007 Combustion Institute. All Rights Reserved.