This collection of papers from the Space Telescope Science Institute Symposium on massive stars addresses the many aspects of astrophysics in which these stars play an important role. Review papers are presented from both observational and theoretical work by world experts in the study of these rare stars. Topics discussed include star formation in the local and distant universe, the feedback effects of the massive stars, mass loss from massive stars, and explosions of massive stars. The combination of papers produces a comprehensive overview of up-to-date research in the field, making this book an invaluable resource for professional researchers and for students of astrophysics.