A search for long-lived charged particles reaching the muon spectrometer is performed using a data sample of 37 pb−1 from pp collisions at √s=7 TeV collected by the ATLAS detector at the LHC in 2010. No excess is observed above the estimated background. Stable τ˜ sleptons are excluded at 95% CL up to a mass of 136 GeV136 GeV, in GMSB models with N5=3, mmessenger=250 TeV, sign(μ)=1)=1 and tanβ=5. Electroweak production of sleptons is excluded up to a mass of 110 GeV. Gluino R-hadrons in a generic interaction model are excluded up to masses of 530 GeV to 544 GeV depending on the fraction of R-hadrons produced as g-balls.