  We present first results of our simulations of magnetic fields in the
formation of single and binary stars using a recently developed method for
incorporating Magnetohydrodynamics (MHD) into the Smoothed Particle
Hydrodynamics (SPH) method. An overview of the method is presented before
discussing the effect of magnetic fields on the formation of circumstellar
discs around young stars. We find that the presence of magnetic fields during
the disc formation process can lead to significantly smaller and less massive
discs which are much less prone to gravitational instability. Similarly in the
case of binary star formation we find that magnetic fields, overall, suppress
fragmentation. However these effects are found to be largely driven by magnetic
pressure. The relative importance of magnetic tension is dependent on the
orientation of the field with respect to the rotation axis, but can, with the
right orientation, lead to a dilution of the magnetic pressure-driven
suppression of fragmentation.
