  Measurements of the production cross section of top-quark pairs ($t\bar t$)
in $pp$ collisions at $\sqrt{s}$ = 7 TeV are presented using 35 \ipb\ of data
recorded with the ATLAS detector at the Large Hadron Collider. Events are
selected in the single lepton (electron or muon) and dilepton topologies with
multi-jets, and large missing transverse energy. The result is $\sigma_{t\bar
t} = 180 \pm 9\,\mathrm{(stat.)} \pm15 \,\mathrm{(syst.)} \pm 6
\,\mathrm{(lumi.)\,pb}$, which agrees with the Standard Model prediction.
