Mechanical properties of anodic alminum oxides (AAO) were achieved by means of-a scanning electron microscope (SEM), an atomic force microscope (AFM), and indentation measurements. A two-step anodized mesoporous anodic aluminum oxide was successfully fabricated vertically and hollowly. Both microindentation and nanoindentation were carried Out. Localized pop-in can be found during nanoindentation due to the collapse of the beneath cylindrical sturctures. Over a certain load, microindentation may induce radial cracks from the indented edge to outward of the AAO. The underside of the indented AAO sample was milled to figure out the structural changes. (C) 2008 Elsevier B.V. All rights reserved.