Mechanical strength of solid catalysts is one of the most important factors for the reliable and efficient performance of a reactor. Some recent developments on the basic mechanics of solid catalysts are reviewed in this article. The main concepts discussed are the brittle fracture which leads to the mechanical failure of the catalyst pellets, the measurement and statistical properties of the catalyst strength data, the mechanical reliability of the catalyst pellets, the mechanical properties of the catalyst packed beds, etc. For the purpose of an integrated research on catalyst mechanical properties, a multi-scale framework for the mechanics of the fixed bed catalysts is also proposed. The scientific basis for the issues on the catalyst mechanical properties calls yet for further elucidation and advancement. (c) 2007 American Institute of Chemical Engineers.