We study the evolution of the velocity distribution function of interstella
r hydrogen atoms in the heliospheric interface, the region of solar and int
erstellar wind interaction. The velocity distribution is a key tool to eval
uate uncertainties introduced by various simplified models of the interface
. We numerically solve the kinetic equation for neutral gas self-consistent
ly with the hydrodynamical equations for plasma. Neutral and plasma compone
nts efficiently coupled by charge exchange. This interaction disturbs the a
tom velocity distribution, which is assumed to be Maxwellian in the circums
olar local interstellar medium. It is shown that besides "original" interst
ellar atoms, there are three other important atom populations originating i
n the heliospheric interface. We present velocity distribution functions of
these populations in various locations of the interface region and discuss
their kinetic properties.