Multijet measurements with the CMS detector at 7TeV

Measurements sensitive to QCD multijet production are presented, using data from proton-proton collisions at a centre-of-mass energy of 7 TeV collected with the CMS detector at the CERN LHC. Data were collected during the 2010 data-taking period, and correspond to an integrated luminocity of up to $36\ensuremath{\, \rm{pb}^{-1}}$. The dijet azimuthal decorrelations, the hadronic event shapes and the ratio of the 3-jet to 2-jet production cross-sections confront the QCD multijet dynamics at a previously unexplored kinematic regime. The data are compared to the predictions of various QCD Monte-Carlo generators.