Mullite slurries with varying particle size, solid fraction and dispersant content were cast, dried and subsequently compressed to obtain a series of green compacts. The relationship between the theological properties of slurries and pore size distribution of the green compacts was examined. Slip cast bodies obtained from shear thinning slurries have larger total pore volume, which decreases considerably with increasing pressure during post-compression. The ratio of the median pore diameter of the compact to the median particle size is higher on the as-cast bodies obtained from shear thinning slurries than on those from Newtonian ones. The difference of the ratio becomes smaller with increasing post-compressive pressure. The agglomerates in the slurry affect the dried green casts and hinder the densification. The effect of agglomerates decreases considerably during subsequent mechanical compaction, yet remains at a compressive pressure as high as 196 MPa.