The operation of a blast furnace is characterized by simultaneous running chemical and physical processes. Hence, the influence of parameters like pressure, temperature and gas composition on the reduction behaviour of the iron bearing minerals cannot easily be presented in a simplified form, e.g. a reduction test with only CO as reducing agent. In the course of this work experiments on the reduction behaviour of iron ores were made with a vertical retort furnace. The mass loss due to the removal of oxygen in the iron bearing material was recorded. The morphologic changes of the microstructures before and after the reduction process were examined by means of metallographic sections of samples. The goal of this work was to evaluate the influence of both gas composition and temperature profile on reducibility and to determine optimized conditions for the operation of a blast furnace.