Track reconstruction with first collision data in CMS

The first LHC collisions at center of mass energies of 900 GeV and 2.36 TeV were recorded by the CMS detector in December 2009. The trajectories of charged particles produced in the collisions were reconstructed using the all-silicon tracker and t heir momenta were measured in the 3.8T solenoidal magnetic field. Reconstructed tracks are used to determine the position of the primary interaction vertex in the event and to monitor the position of the colliding beams. The tracks have been used further to reconstruct the hadronic decays of several mesons, including K^0s, @L, and @F. The performance of track reconstruction has been measured in the data and is compared to the expectation from simulation.