Since the beginning of the last century, many studies have been performed in order to improve our understanding on the milling process. Recently, Mishra and Rajamani (1992) applied the Discrete Element Method (DEM) to solve the milling problem. Since then, this method gained considerable success due to its ability to predict load motion and power draw by tumbling mills as affected by operating conditions. The application of this method at an industrial stage requires a more rigorous validation in order to produce realistic output. Lifter profiles play a key role in the performance of tumbling mills since they influence the motion of mill charge. Since lifters change profiles during their useful life due to wear, the performance of tumbling mills will correspondingly vary as a function of time. There is therefore a need to predict forces and wear on mill lifters in order not only to chose or design an initial lifter profile which optimizes tumbling mills performance over the lifters’ useful life but also to evaluate lifter replacement time and type and also modifications which can be performed on lifters and/or operating mill conditions in order to extend the lifters’ useful life. Despite the importance related to this subject, few works has been done in this field. In this thesis, we firstly assess the ability of the Discrete Element Method to model the tangential and normal forces exerted by the mill charge on lifters. Data from an experimental two-dimensional mill designed in order to record the normal and tangential forces exerted on an instrumented lifter were available. The measured results obtained at different speeds and percentages of filling have been compared to the Discrete Element Method simulated results in the same conditions. A good agreement has been found between the experimental and the simulated results in terms of toe, shoulder positions and amplitude of forces. After this validation of the DEM, we secondly assess the ability of this method to predict the wear of lifters in dry milling conditions. We derived a mathematical wear equation describing the removal of materials from lifters which takes into account all types of wear occurring in dry milling environment. We introduce a new approach to implement this equation in the DEM code in order to produce realistic simulated profiles. Our new method developed has been tested against laboratory and industrial data of evolving lifter profiles due to wear. Good agreement has been found between the simulated and the measured profiles. The variation of the load behaviour as a function of lifter wear in industrial tumbling mills studied was also investigated in this thesis. The objectives were to improve the understanding of the grinding process and quantify the variation of load behaviour as a function of lifter wear. Lifter modifications were also explored in order to extend lifters useful life. An attempt was also made in this thesis to derive, from the description of the load behaviour, equations in order to predict the wear of lifters without using the Discrete Element Method. Equations derived show the difficulty to use this approach. Success in this case was achieved only in a particular case where no significant changes occur in the load behaviour as a function of lifters wear. This finding confirms the DEM as the adequate tool to model forces and wear of tumbling mill lifters. The results obtained are of great economical significance since they can improve the profitability of mineral processing plants. A step forward in the use of the DEM not only to design milling equipments but also to improve the understanding, optimise and quantify the change occurring as a function of lifters wear was achieved.