The effect of polyethylenimine (PEI) on preparing macroporous ZrO2 materials via heterocoagulation coating process was investigated, using ZrO2 nanoparticles as the building materials and polystyrene spheres as the organic templates. When PEI was applied to modify the surface charge of ZrO2 nanoparticles, it was found that 40-50% of initial PEI amount remained excess in the suspensions. Adsorption of excess PEI on the surface of polystyrene spheres resulted in partial coating of the polystyrene spheres by ZrO2 nanoparticles at 1 wt% PEI and even no coating at 3 wt% PEI. Microstructure studies revealed that ZrO2 ceramics prepared without using PEI had quite ordered macropores, while the ZrO2 framework was partially collapsed at 1 wt% PEI and disordered macropores were observed at 3 wt% PEI. (C) 2005 Springer Science + Business Media, Inc.