  We present results from the first hydrodynamical star formation calculation
to demonstrate that brown dwarfs are a natural and frequent product of the
collapse and fragmentation of a turbulent molecular cloud. The brown dwarfs
form via the fragmentation of dense molecular gas in unstable multiple systems
and are ejected from the dense gas before they have been able to accrete to
stellar masses. Thus, they can be viewed as `failed stars'. Approximately three
quarters of the brown dwarfs form in gravitationally-unstable circumstellar
discs while the remainder form in collapsing filaments of molecular gas. These
formation mechanisms are very efficient, producing roughly the same number of
brown dwarfs as stars, in agreement with recent observations. However, because
close dynamical interactions are involved in their formation, we find a very
low frequency of binary brown dwarf systems ($\lsim 5$%) and that those binary
brown dwarf systems that do exist must be close $\lsim 10$ AU. Similarly, we
find that young brown dwarfs with large circumstellar discs (radii $\gsim 10$
AU) are rare ($\approx 5$%).
