  A blind analysis searching for the decay Bs0 -> mumu has been performed using
proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the
ATLAS detector at the LHC. With an integrated luminosity of 2.4 fb^(-1) no
excess of events over the background expectation is found and an upper limit is
set on the branching fraction BR(Bs0 -> mu mu) < 2.2 (1.9) x10^(-8) at 95%
(90%) confidence level.
