Interest in characterizing the mechanical properties of porous materials at micro-/nanometer scales has increased due to recent development of micro-/nanosystems. Depth-sensing indentation (DSI) systems, also referred to as nanoindentation, are strong tools for performing indentation measurements. The load-displacement curves of SiAlON-based porous ceramics were measured under different peak load (200-1800 mN). The most commonly used Oliver-Pharr method was used to analyze the unloading segments of these curves. The experimental results revealed that the dynamic hardness (H-d) and reduced elastic modulus (E,) exhibit peak-load dependence, i.e., indentation size effect (ISE). Such peak-load dependence requires calculation of the load-independent hardness (H-LI) and elastic modulus (E,). The experimental hardness data were analyzed using Meyer's law, Hays-Kendall's model, the proportional specimen resistance (PSR) model, and the modified PSR (MPSR) model. As a result, the modified PSR model is found to be the most effective one for Hd determination of these SiAlON-ceramics. (c) 2007 Elsevier Ltd. All rights reserved.