  The performance of the Local Trigger based on the drift-tube system of the
CMS experiment has been studied using muons from cosmic ray events collected
during the commissioning of the detector in 2008. The properties of the system
are extensively tested and compared with the simulation. The effect of the
random arrival time of the cosmic rays on the trigger performance is reported,
and the results are compared with the design expectations for proton-proton
collisions and with previous measurements obtained with muon beams.
