  We investigate in this paper the antideuteron flux produced in high energy
collisions of cosmic rays with the interstellar matter. We employ the Monte
Carlo generator DPMJET-III together with the coalescence model to simulate, in
an event-by-event basis, the antideuteron production in cosmic ray collisions
in our Galaxy. Then, we use a diffusion model to calculate the expected flux.
We find a secondary antideuteron flux at the Earth which is approximately a
factor of two smaller than in previous calculations.
