Intended as an introduction to the mechanical alloying technique used in developing different materials systems, this work is suitable for undergraduate and post-graduate students, and also for scientists and engineers who wish to gain some understanding of the process. It begins with a brief introduction providing historical background to the development of the mechanical alloying process. There are several different types of ball mills available, some of them specially designed for the mechanical alloying process. Since the resultant materials are milling-intensity and milling-temperature dependent, ball mills should be carefully selected in order to obtain the desired materials and structures. The actual mechanical alloying process is considered and, as it is essential to understand the use of processing-control agents, the physical properties of some commonly used agents are listed. There is coverage of the formation of new materials and mechanical alloying of Al, Ti and Mg alloys and their intermetallics, and the formation of composite materials using this technique is also discussed in detail. Several examples of the mechanical alloying of amorphous materials, an important group of engineering materials where mechanical alloying is commonly employed, are given, and there is a look at the characterization of the alloyed powders.