  We have selected archival observational data for several O and B trapezia in
the Milky Way. For each of the main components of the trapezia we obtained
transverse velocities from the historical separation data. With this
information, and with the stellar masses of the main components, we studied the
dynamical evolution of ensembles of multiple systems mimicking each one of the
trapezia. For this purpose we conducted numerical $N-$body integrations using
the best available values for the masses, the observed positions and {\bf
transverse} velocities, randomly generated radial velocities, and random
line-of-sight ($z$) positions for all components. Random perturbations were
assigned to the observed quantities, compatible with the observational errors.
A large fraction of the simulated systems ({\bf between 70 and 90 percent})
turned out to be unbound. The properties of the evolving systems are studied at
different values of the evolution time. We find that the dynamical lifetimes of
both the bound and unbound seems to be quite short, of less than 10~000 yr for
the unbound systems, and of 10~000 to 20~000 yr for the bound systems. The end
result of the simulations is usually a binary {\bf with semiaxes of a few
hundred AU} sometimes a triple of hierarchical on non-hierarchical type.
Non-hierarchical triples formed during the integrations (which are dynamically
unstable) were found to have much longer lifetimes, of 250~000 to 500~000 yr.
The frequency distributions of the major semi-axes and eccentricities of the
resulting binaries are discussed and compared with observational properties of
binary systems from the literature.
