This paper introduces scenario methods and a framework for envisioning global futures. It depicts contrasting world development scenarios, all compatible with current patterns and trends, but with sharply different implications for the quest for sustainability in the twenty-first century. Three broad scenario classes are depicted—Conventional Worlds, Barbarization, and Great Transitions—which are characterized by, respectively, essential continuity with current patterns, fundamental but degenerative social change, and fundamental and progressive social transformation.