Titanium diboride is being evaluated as a replacement of SiC in metal/ceramic composites for thermal management. Albeit these composites are produced by gas pressure infiltration, no study of the process is available. This work presents an analysis of the threshold pressure for infiltration of Al into TiB2 compacts and of the infiltration kinetics. Particles of diameters 14 and 20 mu m, and spans of 1.62 and 1.77, were packed obtaining a volume fraction of 0.63. The compacts were infiltrated in air with pure Al at 700 A degrees C. Despite of the fact that the average particle radii differ in a 50%, the threshold pressure for the coarser particles is only a 4% lower, while intrinsic compact permeabilities (derived from infiltration of a wetting organic liquid) are identical. The origin of this apparently odd behavior is the almost identical specific surface areas that those two particles have. Contact angles derived from infiltration experiments are shown to be compatible with sessile drop results.