The effects of some material variables (particle size and moisture content) on the tensile strength and disintegration time of tableted standard microcrystalline cellulose (MCC, Avicel) and a silicified brand (SMCC, Prosolv) were studied. Three particle size fractions were employed, after equilibration in three levels of environmental relative humidity (RH%), and the tensile strength and disintegration time were determined at different levels of total tablet porosity or packing fraction (p(f)). The MCC grade or silicification affects the moisture sorption and the packing during tapping as well as the particle deformation (yield pressure, P(y)) during tableting. There was a slight increase in the tensile strength but a marked increase in the disintegration time of Prosolv compared with Avicel in the p(f) range 0.7-0.9, which corresponds the range for pharmaceutical tablets. These increases are explained in terms of the range and magnitude of the interparticle forces developed and the interparticle separation. Despite the higher moisture content of Prosolv after equilibration compared with Avicel, compression of Prosolv results in higher P(y), in tablets of higher energy of interparticle bonding, longer interparticle separation, and extended disintegration compared with Avicel. The incorporated SiO(2) is thought to play the role of barrier or sink for the moisture sorbed, but only for RH up to 52%, which is a moisture content range less than twice that of tightly bound water. At higher RH (72%), the incorporated SiO(2) does not increase the P(y), but reduces the energy of interparticle bonding and the interparticle separation because of its probable saturation. The latter, in turn, results in more extended disintegration times due to reduced uptake of water into the tablets and to the probable reduction of water available for the deployment of the microcrystalline cellulose activity as disintegrant.