We study evolution of the velocity distribution function of interstellar
neutral gas in the heliospheric interface, the region of the solar and
interstellar wind interaction.We numerically solve the kinetic equation
for neutral gas self-consistently with hydrodynamical equations for plasma.
Neutral and plasma components interact by charge-exchange. This interaction
disturbs of atom velocity distribution, which is assumed to be Maxwellian
in the circumsolar interstellar medium. To describe a complex of velocity
distribution of interstellar atoms in the heliospheric interface we introduce
three atom populations in addition to the primary interstellar neutrals.
We present velocity distributions of these populations and discuss their