  The ability to identify jets containing B hadrons is important for the
high-pT physics program of a general-purpose experiment such as ATLAS.
b-tagging is in particular useful for selecting very pure top quark samples,
for studying standard model or supersymmetric Higgs bosons which couple
preferably to heavy objects, for vetoing backgrounds for several physics
channels and finally for searching for new physics beyond the standard model
like supersymmetric particles or heavy gauge bosons. After a review of the
algorithms used to identify b-jets, their anticipated performance is discussed
as well as the impact of selected critical ingredients such as residual
misalignments in the tracker. The prospects to measure the b-tagging
performance in the first few hundreds pb-1 of data with di-jet events as well
as ttbar events are presented. Finally three different physics use cases of
b-tagging are summarised.
