MCFOST is a 3D continuum and line radiative transfer code based on an hybrid Monte Carlo and ray-tracing method. It is mainly designed to study the circumstellar environment of young stellar objects, but has been used for a wide range of astrophysical problems. The calculations are done exactly within the limitations of the Monte Carlo noise and machine precision, i.e., no approximation are used in the calculations. The code has been strongly optimized for speed.

MCFOST is primarily designed to study protoplanetary disks. The code can reproduce most of the observations of disks, including SEDs, scattered light images, IR and mm visibilities, and atomic and molecular line maps. As the Monte Carlo method is generic, any complex structure can be handled by MCFOST and its use can be extended to other astrophysical objects. For instance, calculations have succesfully been performed on infalling envelopes and AGB stars. MCFOST also includes a non-LTE line transfer module, and NLTE level population are obtained via iterations between Monte Carlo radiative transfer calculations and statistical equilibrium.