  We investigate the spectroscopic characteristics of the optical components of
Be/X-ray binary systems, using data collected during our seven-year monitoring
campaign. We find examples of major changes in the emission line profiles
associated with Type II X-ray outbursts, later developing into V/R variability
cycles. We show that the time-scales for V/R variability in Be/X-ray transients
extend from a few weeks to years and interpret all these changes as due to the
presence of global disruptions of the axisymmetric density distribution in the
extended envelopes of the Be stars in these systems. The association between
X-ray outbursts and V/R variability, the occurrence of very fast changes and
the very short quasi-periods of variability displayed by Be/X-ray binaries lead
us to conclude that the presence of the neutron star is an important factor
affecting the dynamics of the disc-like envelopes. The interaction between the
compact companion and the disc would explain the correlation between H-alpha
strength and orbital period recently found. The characteristics of the V/R
cycles are, however, mainly independent of the binary parameters.
