Great expectations were expressed about the future of high power diode lasers for direct materials processing applications, when they have been introduced in the mid-nineties. Nevertheless, based on their technology, there are physical limitations, especially if beam quality is considered: Kilowatt power must be generated from individual elements, which do not provide more than a few watts for the time being, if they shall last for a reasonable time; such elements are incoherently combined. In this article the technology will be analyzed about their potential and a comparison with "conventional" high power lasers will be performed. Fortunately not all laser materials processing techniques require extremely high power density, i.e. high beam quality, but rather need a larger spot or a spot with a special shape. Such applications are the niches for the highly efficient and reliable diode lasers. In this context, high power diode lasers have proven to be a perfect supplement to the existing CO2 and Nd:YAG materials processing lasers rather than a competitor for them.