With the luminosity upgrade of the LHC machine, the Muon System of the ATLAS experiment at CERN will also need
a detector upgrade in the highest rapidity region. An R&D activity has started with the aim to develop large detectors
based on the bulk-Micromegas technology to be used in the ATLAS Muon Spectrometer. Micormegas detectors are good
candidates to construct large muon chambers that combine trigger and tracking capability and can cope with the high particle
rates expected at SLHC. A medium size Micromegas prototype has been built and evaluated in the laboratory and
in beam tests at CERN. Basic ideas of the ATLAS Muon upgrade using Micromegas will be presented.