Abstract
Accurate determinations of Wolf-Rayet (WR) mass-loss rates are an important goal of hot star research, and one in which colliding wind binaries will play ar important role in future. The most common current method of determining mass-loss rates uses thermal radio emission, and current uncertainties in our understanding of this method as well as new results on radio emission from colliding wind systems will be discussed. New ASCA spectra of gamma Velorum will be presented and a new method of determining WR mass-loss rates using X-ray spectroscopy in conjunction with hydrodynamic models of colliding winds will be described. The determined value for the WR component of gamma Vel is MWR = 2-3 x 10-5 Solar Mass/yr.
