We have characterized the Underlying Event in pp collisions at √ s = 0.9 and 7 TeV by measuring the number density, the summed p T distribution and the azimuthal correlation of charged particles with respect to the leading particle. The analysis is based on about 6 · 10 6 minimum bias events at √ s = 0.9 TeV and 25 · 10 6 events at √ s = 7 TeV collected during the **data** taking periods from April to July 2010. Measured **data** have been corrected for detector related effects; in particular we applied a data-driven correction to account for the misidentification of the leading track. The fully corrected final distributions are compared with Pythia 6.4, Pythia 8 and Phojet, showing that pre-LHC tunes have difficulties describing the data. These results are an important ingredient in the required retuning of those generators.