The rheological behavior of concentrated ZnO-Al2O3 aqueous suspensions has been studied in order to obtain an ultrahigh-density ZnO-Al2O3 composite ceramic target by slip casting. The influence of the mass fraction of polyacrylic acid (PAA) on the fluidity of slurries and the density and strength of the green and sintered bodies was investigated. The slurries exhibited a near-Newtonian flow behavior and had a lower viscosity with 0.3 wt% PAA. The excess of PAA enhanced the green strength and the density and strength of the sintered bodies. An ultrahigh density sintered body (> 99.7% theoretical density) could be obtained after pressureless sintering at 1400 degrees C. The Al species were well distributed in the sintered bodies, which showed a homogeneous, defect-free microstructure with no abnormal grain growth.