This paper describes generally the tool steels, the properties they require, and the general influence of the alloying elements. From tool steels, a high speed steel, which is part of high-alloyed steels is specifically described. The pseudobinary diagram and metallographic properties of high speed steel, its working conditions, heat treatment and examples of use are described. The introductory part describes the emerging and historical development of fast steel. In the following section, the division of the tools to their working temperatuers and a more detailed description of their purpose are listed, also there is listed the divison of tool steels to their working temperatures and their degree of legacy. The requirements for the properties of tool materials are also given and the most important properties of tool steels (general properties, special properties and production properties) are also described. After that, the general influence of the alloying elements is explained, the classification of the alloying elements used and their impact on the properties of tool steels are given. In the following, more detailed description of high speed steels is given in terms of their working conditions, pseudobinary diagram and metallographic characteristics. Furthermore, it describes how all heat treatments are subjected to high speed steel and how they affect its properties and structure. At the end of the work, examples of high speed steels use are given, as well as insights into the basic principles of fast-moving steel.