  We derive the quantum Boltzmann equation (QBE) of composite fermions at/near
the $\nu = 1/2$ state using the non-equilibrium Green's function technique. The
lowest order perturbative correction to the self-energy due to the strong gauge
field fluctuations suggests that there is no well defined
Landau-quasi-particle. Therefore, we cannot assume the existence of the
Landau-quasi-particles {\it a priori} in the derivation of the QBE. Using an
alternative formulation, we derive the QBE for the generalized Fermi surface
displacement which corresponds to the local variation of the chemical potential
in momentum space. {}From this QBE, one can understand in a unified fashion the
Fermi-liquid behaviors of the density-density and the current-current
correlation functions at $\nu = 1/2$ (in the long wave length and the low
frequency limits) and the singular behavior of the energy gap obtained from the
finite temperature activation behavior of the compressibility near $\nu = 1/2$.
Implications of these results to the recent experiments are also discussed.
