Copyright MRS 2006.-- Final full-text version of the paper is available at: http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=5725&DID=166361&action=detail.The adequacy of instrumented Vickers depth-sensing microindentation to determine Young's modulus of alumina-based ceramics was analyzed. Monophase alumina materials and alumina + 10 vol% aluminium titanate composites, with different microstructures, were tested to determine the effect of microcracking. The curve's load-depth penetration of the indenter together with the observation of the imprints by scanning electron microscopy were used to analyze the behavior of the materials. Maximum stiffness was determined from the derivatives of the load-depth curves during unloading. The areas of the imprints measured optically were more representative of the behavior of the materials than the areas calculated from depth-penetration measurements. The formation of microcracks affected the shape of the unloading portion of the curves. Significant differences between the values of Young's modulus determined for different materials and definite relationships between the microstructural parameters of the materials and the Young's modulus were found.This work was supported in part by the European Community's Human Potential Programme under Contract No. HPRN-CT-2002-00203 (SICMAC), by Project Nos. CICYT MAT2003-00836 and CAM GRMATO707-2004, and by Grant No. CSIC I3P-BPD2001-1 (Spain).Peer reviewed