Due to the large top quark production cross section at the LHC, ATLAS
experiment is expected to have enough statistics to measure top quark 
properties even at initial luminosities. The main focus of my 
presentation will be on the measurements of top quark pair cross 
section. I will present the current situation with top quark cross 
section measurements at Dzero experiment and recent studies performed 
in ATLAS with emphasis on measurements with data that will be collected 
in the first year of the LHC run. The potential of using the top quark 
events for the b-tagging calibration will be also briefly discussed.