  B[e] supergiants (B[e]SGs) are emission-line objects, presumably in a
short-lived phase in the post-main sequence evolution of massive stars. Their
intense infrared excess emission indicates large amounts of warm circumstellar
dust, and the stars were longtime assumed to possess an aspherical wind
consisting of a classical line-driven wind in polar direction and a dense, slow
equatorial wind dubbed outflowing disk. The general properties obtained for
these disks are in line with this scenario, although current theories have
considerable difficulties reproducing the observed quantities. Therefore, more
sophisticated observational constraints are needed. These follow from combined
optical and infrared spectroscopic studies, which delivered the surprising
result that the circumstellar material of B[e]SGs is concentrated in multiple
rings revolving the stars on stable Keplerian orbits. Such a scenario requires
new ideas for the formation mechanism, in which pulsations might play an
important role.
