  High mass X-ray binary luminosity function (XLF) is an important tool for
studying binary evolution processes and also the mass loss and consequent
evolution in massive stars. We calculate the XLF for neutron star binaries
using the standard scenario for formation and evolution of these systems. A one
to one relation between primordial binary parameters and the HMXB parameters is
established. The probability density function is then transformed using the
standard Jacobian formalism. It is shown that the model successfully explains
some basic properties of the observed XLF.
