During the spaceflight of the first Austrian astronaut on board the Soviet space station MIR in October 1991, the experiment AUDIMIR was successfully performed as a part of the Austrian scientific program. AUDIMIR started from the assumption that, in the absence of gravity, orientation by acoustic cues would play a much more important role for a human being than on Earth. The experiment was designed to verify this assumption, and thus to verify the usefulness of binaural audio technology for communication systems of future spacecrafts and spacestations. The first goal of the experiment was the investigation of the accuracy of localization under conditions of microgravity. The second part should, for the first time ever, investigate the role of directional hearing as part of the human orientation system at microgravity by presenting moving sound sources to the subject. The whole experiment was performed in a virtual acoustic environment comprised of headphones and a digital signal processor. Visual influences were excluded by the astronaut having his eyes closed. The binaural processing of the test signals was done ‘‘live’’ during the actual experiment. This opened the possibility of adaptive control of the experiment procedure. To get optimum spatial performance, the subjects individual HRTF’s were used.