Optical pyrometers provide many advantages over intrusive measuring techniques in determining the spatial and time varying temperature distribution of fast rotating components in gas turbines. This paper describes the development and evaluation of a versatile high-resolution pyrometer system and its application to radial turbine rotor temperature mapping as has been done in a R&D project at the Technical University Berlin under funding from Siemens Power Generation (KWU). The development goal was a pyrometer system with a temporal resolution of 1 μs, a minimum field of view of 1 mm, and a measurement range from 600 to 1500°C. A prototype of the pyrometer system has been built and tested at the small gas turbine test facility of the Technical University Berlin. The system yielded excellent results with respect to measurement uncertainty, resolution, and reliability. Finally, measurement results obtained with the new system on a radial turbine rotor and on a heavy duty industrial gas turbine are compared with measurements conducted with a commercially available turbine pyrometer system.