Although much is known about the nature of winds from hot stars and giants and supergiants with spectral types earlier than K, there is still much to be learned regarding the mass-loss process in cool, late-type stars. We will review the current state of research, with particular reference to observations and modelling of mass-loss from giant stars in symbiotic systems.

The transition from early Of stars to WN type objects is poorly understood. O-type supergiants with emission lines (OIf) are considered to be intermediate between these two classes. The scope of this paper is to investigate the spectral variability of three Of supergiants. We constituted spectral time series of unprecedented quality for our targets (∼ 200 spectra in total), essentially in the b...