Abstract: The disclosure relates to a method for determining the compressive character of an olefin polymerisation catalyst, comprising subjecting particles of an olefin polymerisation catalyst to micro-compression testing to obtain crushing strength data of the particles of the olefin polymerisation catalyst to determine the compressive character of the olefin polymerisation catalyst. The disclosure further re later to a method for evaluating the quality of an olefin polymerisation catalyst, comprising determining the compressive character of the olefin polymerisation catalyst, and evaluating the quality of the olefin polymerisation from the information obtained from the determination of its compressive strength. The disclosure still further relates to a method for predicting the performance of an olefin polymerisation catalyst in an olefin polymerisation process from its compressive strength descriptors, characterized in that the compressive character of the olefin polymerisation catalyst is determined as disclosed.