  We present results from our numerical simulations of collapsing massive
molecular cloud cores. These numerical calculations show that massive stars
assemble quickly with mass accretion rates exceeding 10^-3 Msol/yr and confirm
that the mass accretion during the collapsing phase is much more efficient than
predicted by selfsimilar collapse solutions, dM/dt ~ c^3/G. We find that during
protostellar assembly out of a non-turbulent core, the mass accretion reaches
20 - 100 c^3/G. Furthermore, we explore the self-consistent structure of
bipolar outflows that are produced in our three dimensional magnetized collapse
simulations. These outflows produce cavities out of which radiation pressure
can be released, thereby reducing the limitations on the final mass of massive
stars formed by gravitational collapse.
  Additional enhancement of the mass accretion rate comes from accretion along
filaments that are built up by supersonic turbulent motions. Our numerical
calculations of collapsing turbulent cores result in mass accretion rates as
high as 10^-2 Msol/yr.
