Mechanical strength of catalyst carrier beads and used catalyst particles was measured by compression of the particles between two platens and analysed by Weibull's method. This statistical method is well adapted to brittle materials such as the alumina particles used in this work, as the failure is affected by pre-existing flaws. It enables a detailed quantitative analysis of the effects of process parameters such as macroporosity, second phase and drying procedure and of macrodefects such as air bubbles on particle strength. It is also shown that the Weibull analysis can detect a multi-modality within a sample. The methodology outlined here has been used to optimize the manufacturing process I of catalyst carrier beads, resulting in a significant improvement in the catalyst strength.