A good measurement of high momentum muons is very important for the search for new high mass resonances. The ATLAS Muon Spectrometer is designed to achieve a momentum resolution of 10% for muons with a transverse momentum of 1 TeV. In this momentum range,  one of the main sources of uncertainty originates from the misalignments between the chambers of the spectrometer. The curvature of such muons amounts to about 500 micrometers in the ATLAS toroidal magnetic field. It is thus necessary to determine the positions of the chambers with a precision better than 50 micrometers.
The alignment system of the ATLAS muon spectrometer relies on measurements given by optical sensors placed on the chambers combined with track-based algorithms in order to provide a reference geometry. In year 2011, dedicated collision runs have been recorded for the validation of the alignment. Performances close to nominal have been obtained in most parts of the detector. This poster exposes the strategies developed for the alignment, the validation methods and the performances reached.