Cerchar abrasivity index (CAI) test is widely used to estimate the tool life and wear in various excavation equipment in mining and tunneling projects. The aim of this study is to analyze the effect of various factors related to the CAI testing procedure. Particularly, sensitivity of CAI results is investigated due to variation of certain testing parameters, including the type of apparatus used, wear flat measurement methods, specimen surface conditions and stylus hardness. Relationship between CAI and certain testing parameters, and its repeatability are also investigated through statistical analyses of a series of CAI tests results obtained from twenty-one selected rock specimens.,Results: show little variation between the type of apparatus used and between the selected wear flat measurement methods. Nevertheless, there is a significant large variation in CAI values according to the changes in specimen surface conditions and the hardness of stylus used. The results show that with an increase in the hardness of the steel stylus the CAI values decrease differently in accordance with the rock type tested.