  The new CDFII detector incorporates a Time-of-Flight detector (TOF),
employing plastic scintillator bars and fine-mesh photomultipliers. Since
August 2001 the TOF system has been fully instrumented and integrated into the
CDFII data acquisition system. With a design goal of $100 ps$ resolution the
TOF system will provide at least two standard deviations separation between
$K^{\pm}$ and $\pi^{\pm}$ for momenta $p<1.6 GeV/c$, complementing low momentum
particle identification by means of the specific ionization energy loss
measured in the drift chamber. We describe the design of the TOF detector and
discuss the current status of its calibration and initial performances. Finally
we review the expected impact of the TOF detector in the flavor tagging of
neutral $B_S$ meson.
