  We derive and solve kinetic equations for leptogenesis within the Closed Time
Path (CTP) formalism. It is particularly emphasised how the procedure of real
intermediate state subtraction familiar from the Boltzmann approach is realised
within the CTP framework; and we show how in time-independent situations, no
lepton asymmetry emerges, in accordance with the CPT-theorem. The CTP approach
provides new quantum statistical corrections from evaluating the loop
integrals. These lead to an enhancement of the asymmetry that is originating
from the Bose statistics of the Higgs particles. To quantify this effect, we
define and evaluate an effective CP-violating parameter. We also solve the
kinetic equations and show explicitly that the new quantum statistical
corrections can be neglected in the strong washout regime, while, depending on
initial conditions, they can be very sizable for weak washout.
