The anodic oxidation technique was successfully carried out to fabricate porous ZnO films. Energy dispersive X-ray and scanning electron microscope indicated that the anodic oxidation time was the key factor to control surface pore density, which varied from 0.2 +/- 0.01% to 59.8 +/- 5.4%. The cytotoxicity study indicated that porous ZnO films displayed the pore density-dependent cytotoxicity on the metabolism and spread of NIH 3T3 fibroblasts. The photocatalytic activity of porous ZnO films was investigated by employing methyl orange as the model compound and it was pore density-dependent. In view of the relatively facile separation property and subsequently the decrease of toxic side effects to the environment of film-form ZnO products compared to powder products, this study suggested the superior potential of the former as the photocatalyst. (C) 2011 Elsevier B.V. All rights reserved.