  We have searched for periodicity in the photometric and spectroscopic
variations of the enigmatic star HD 101584 and found a long-term variability on
a typical time scale of 1700 days (4.7 years) and a highly significant period
of 218+-0.7 day. This period is most prominently present in the photometric
indices which are a measure for the Balmer jump (Geneva d and Stromgren c). The
Doppler velocities of the high-excitation photospheric absorption lines (HeI
and CII) seem to be variable with the photometric period. Our data favor the
218 day period for the Doppler velocities with a small probability that the
true period is 436 days. We argue that HD 101584 is a close (highly) eccentric
218 day binary system with a low-mass unseen secondary. The photometric and
Doppler variations are attributed to changes in the velocity law and mass-loss
rate of the stellar wind which lead to asymmetric line profiles and a phase
dependent Balmer discontinuity. Binary interaction is responsible for the
changes in velocity law and mass-loss rate leading to the observed phenomena.
