  Numerical simulations of planetesimal accretion in circumprimary and
circumbinary orbits are described. The secular perturbations by the com- panion
star and gas drag are included in our models. We derive limits on the
parameters of the binary system for which accretion and then planetary forma-
tion are possible. In the circumbinary case we also outline the radial distance
from the baricenter of the stars beyond which accumulation always occurs. Hy-
drodynamical simulations are also presented to validate our N-body approach
based on the axisymmetric approximation for the gas of the disk.
