  Proper motion measurements of the cool and ultracool populations in the Upper
Scorpius OB association are crucial to confirm membership and to identify
possible run-away objects.
  We cross-match samples of photometrically selected and spectroscopically
confirmed cool and ultracool (K5<SpT<M8.5) candidate members in the Upper
Scorpius OB association using the literature and the USNO-B and the UCAC2
catalogues. 251 of these objects have a USNO-B and/or UCAC2 counterpart with
proper motion measurements.
  A significant fraction (19 objects, 7.6+-1.8%) of spectroscopically confirmed
young objects show discrepant proper motion. They must either belong to
unidentified coincident foreground associations, or originate from neighboring
star forming regions or have recently experienced dynamical interactions within
the association. The observed accretor and disc frequencies are lower among
outliers, but with only 19 objects it is unreliable to draw firm statistical
conclusions. Finally, we note that transverse velocities of very low mass
members are indistinguishable from those of low mass members within 4km/s
