Prospects for Higgs bosons searches with ATLAS, Part I: Higgs Decays to Gauge Bosons. The results presented are based on the ATLAS 14 TeV analysis, the details can be found in CERN OPEN 2008-020, arXiv:09010512. Page 2: the outline. The talk is on the SM H -> gamma gamma, ZZ and WW. In addition H+ -> tau nu. The Higgs decays for fermions are discussed in the talk by M. Schumacher. Page 3 describes the improvements in the Higgs studies at the LHC: details Geant-4 simulations, new (N)NLO Monte Carlos, new approaches to match parton shower matrix elements and more detailed and better understood reconstruction methods. Page 4 described the ATLAS detector components. Page 5 shows the most SM Higgs production mechanisms at the LHC. Page 6 shows the most promising SM Higgs decays branching ratios for Higgs boson searches at the LHC, as a function of the Higgs boson mass. Page 7 shows the prospects for a light Higgs boson search at the LHC, comparing the rates and the most favorable search channels to the Tevatron. Page 8 describes the early data analysis preparation strategies of the ATLAS collaboration. Page 9 describes an example of data driven background estimation methods in ATLAS. Further details could not be shown as the results were not yet approved by the ATLAS collaboration. Page 10 presents the ATLAS search strategy for Higgs -> gamma gamma Page 11 compares the signal in Higgs -> gamma gamma to its reducible and irreducible backgrounds and explains the strategy for jet faking photon rejection. Page 12 shows some details of the H -> gamma gamma search strategy, relying on the Higgs vertex reconstruction and on the understanding of photon conversion. Page 13 shows the prospects for the Higgs signal observation in the H->gamma gamma channel for 10/fb of integrated luminosity. Page 14 describes the selection of lepton final states for H->4 leptons search with ATLAS. Page 15 explains 2 of background rejection methods exploited in the H->4l search, mainly calorimeter and track isolation, in addition to the transverse impact parameter significance. Page 16 shows the significance that can be expected in the H->4l 30/fb of integrated luminosity. Page 17 introduces the search strategy for H->WW->2l+MET, exploiting both the gluon fusion process and the vector boson fusion process. Page 18 explains the 2 main discriminant used in the H->WW->el+MET search, namely the spin correlation between the lepton and characteristic signature of the forward jet tagging and the central jet veto in vector boson fusion. Page 19 shows the significance that can expected in the H->WW->2l+MET for 10/fb of integrated luminosity. Page 20 describes the ATLAS combined discovery potential as a function of the Higgs boson mass and of the integrated luminosity. Page 21 shows the combined exclusion limit that can be achieved with ATLAS as function of the Higgs boson mass and of the integrated luminosity. Page 22 introduces the charged Higgs production and decays mechanisms favorable at the LHC. Page 23 discusses the charged Higgs decay channels studied in ATLAS and shows the discovery prospects for a light charged Higgs and for a heavy charged Higgs, for various integrated luminosities. Page 24 shows the the combined exclusion limit and discovery potential for the charged Higgs at the LHC. A discussion on H+ -> SUSY as a way to cover the "wedge region" is presented. Pages 25-30 describe the ATLAS efforts to prepare Higgs cross-sections and decay branching ratios as function of center of mass energy for SM and MSSM Higgs bosons, including the most recent calculations available. The idea is to prepare and made available the tools needed to calculate quickly the Higgs production cross sections at different center of mass energies (using the most recent calculations available) since we do not know for sure at the which energies the LHC will be operating. Page 31 present the summary and conclusions of the talk.