  We study to which extent planetesimal accretion is affected by the perturbing
presence of a compagnon star. We concentrate on one crucial parameter: the
distribution of encounter velocities within the planetesimal swarm. We
numerically explore the evolution of this parameter taking into account the
secular perturbations of the binary and friction due to the very likely
presence of gas in the disk. $<\Delta v>$ maps are derived, for planetesimals
of different sizes, for a total of 120 binary configurations (eccentricity eb
and separation ab). We identify for each case 3 different accreting behaviours.
1) In regions where no significant dV increase is observed, ``classical''
(i.e., single-star) accretion is possible. 2) In regions where $dV>v_{ero}$,
the threshold velocity above which all impacts are eroding, no accretion is
possible and planet growth is stopped. 3) In between these 2 limiting
behaviours, a large fraction of binary configurations leads to significant dV
increase, but still below the erosion threshold. In this intermediate case,
planetesimal growth can occur, but proceeds slower than in the single-star
case, possibly following the so-called type II runaway groth mode.
