  Transport equations for quark matter are derived in the mean field
approximation for the Nambu -- Jona-Lasinio Lagrangian. Emphasis is put on the
chiral limit (zero current quark masses) and the consequences of the chiral
symmetry are investigated in detail. Our approach is based on the spinor
decomposition of the Wigner function. Kinetic equations for the quark densities
and for the spin are derived. We find that the latter is constrained by the
requirement of the axial current conservation.
