ATLAS Monte Carlo generator tunes to LHC data

Monte-Carlo tunes to the first measurements from the LHC, at center-of-mass energies of 900 GeV and 7 TeV, are presented. Measurements of the charged particle multiplicities and of the momentum flow in the underlying event in inelastic pp collisions are used to constrain the model parameters. The tunes aim for consistent descriptions of the new measurements with data from the Tevatron and LEP. The best-fit parameters were obtained using the Professor tool. Details on obtaining these parameters and on systematic checks will be presented.