Liquid Argon (LAr) Calorimeters provide electromagnetic and forward hadronic calorimetry measurements for the ATLAS experiment. Since 2008, all parts of the LAr calorimeters are read out. An overview of the LAr calorimeters, including hardware status and performance of the calibration system and calorimeter trigger, is presented. Results on timing alignment, uniformity and energy flow, extracted from cosmics and collision data, are presented . They indicate excellent performance of the LAr calorimeters 3 months after the start of LHC operation at 7 TeV energy in the center of mass.