Publisher Summary This chapter elaborates the thyristor and related special high-power electronic devices. The extraordinary speed with which semiconductor devices have developed has resulted in a marked decrease in the price of thyristor components despite worldwide inflation. The thyristor is the most widely used device in most power electronics circuits. However, the future will probably see thyristors replaced by transistors and special devices in many fields, a trend that will simplify circuits and reduce costs. Besides the development of the devices themselves, the improvement of auxiliary equipment should result in better performance and reduce the overall size of the circuit. Particularly, important is the development of the cooling method that could contribute to a significant reduction in the size of the thyristor in the not too distant future. The application of power electronics is spreading. It can be foreseen that its future use in cars, household appliances, etc. will be promoted by lower prices. A further application trend is the growing need for regulation of high-power drives.