The evolution of massive stars with mass loss.

The characteristics of mass-loss in massive stars (at least 9 solar masses) are described. An evolutionary model for a constant mass star is defined for reference purposes, along with diagnostic methods for studying stellar winds and parameterizing mass-loss rates in early, late-type and WR stars. Modifications in the internal structure and evolution of massive stars due to mass loss are explored in terms of core and shell H-burning and core He-burning phases. The influence of mass-loss on the location of stellar objects on the HR diagram and on nucleosynthesis processes is considered, as is the possibility that WR stars are the result of massive star mass-loss. Finally, the galactic distribution of O, blue and red supergiant and WR stars is discussed.