  As of today over 40 planetary systems have been discovered in binary star
systems. In all cases the configuration appears to be circumstellar, where the
planets orbit around one of the stars, the secondary acting as a perturber. The
formation of planets in binary star systems is more difficult than around
single stars due to the gravitational action of the companion on the dynamics
of the protoplanetary disk. In this contribution we first briefly present the
relevant observational evidence for planets in binary systems. Then the
dynamical influence that a secondary companion has on a circumstellar disk will
be analyzed through fully hydrodynamical simulations. We demonstrate that the
disk becomes eccentric and shows a coherent precession around the primary star.
Finally, fully hydrodynamical simulations of evolving protoplanets embedded in
disks in binary star systems are presented. We investigate how the orbital
evolution of protoplanetary embryos and their mass growth from cores to massive
planets might be affected in this very dynamical environment. We consider, in
particular, the planet orbiting the primary in the system Gamma Cephei.
