  A search for a heavy Standard Model Higgs boson decaying via H->ZZ->llnunu,
where l=e,mu, is presented. It is based on proton-proton collision data at
sqrt(s)=7 TeV, collected by the ATLAS experiment at the LHC in the first half
of 2011 and corresponding to an integrated luminosity of 1.04 fb^-1. The data
are compared to the expected Standard Model backgrounds. The data and the
combined background expectations are found to be in agreement and upper limits
are placed on the Higgs boson production cross section over the entire mass
window considered; in particular the production of a Standard Model Higgs boson
is excluded in the region 340 < m_H < 450 GeV at the 95% confidence level.
