  The main properties of the observed extrasolar planets are reviewed with
respect to their relevance to the formation scenario of planetary systems.
Results of numerical computations of embedded planets in viscously evolving
disks are presented. Emphasis is given to the accretion and migration process.
New calculations on inviscid disks are shown.
  The second part of the talk concentrates on resonant planetary systems. Among
the observed extrasolar systems there are 3 confirmed cases, Gl 876, HD 82943
and 55 Cnc, where the planets orbit their central star in a low order mean
motion resonance. Results of numerical simulations modeling the formation and
evolution of such systems are presented.
