Research into "discourse synthesis" examines the ways in which writers make use of, and transform, multiple other texts in writing their own. It is intertextual research that has blurred boundaries of various kinds, not only the boundary between the processes of reading and writing but also boundaries across disciplines as well as regions of the world. Guided by a cognitive constructivist perspective, this research into discourse synthesis drew at its origin--and continues to draw now--from multidisciplinary theoretical and empirical work. This article, which establishes the foundations for this research and traces its development, attends to writers' transformations of multiple source texts resulting from operations of organizing, selecting, and connecting. Studies into synthesis writing for varying academic tasks have shown that, by applying these operations to multiple textual sources, writers produce discourses that function as new texts in new contexts. Following a discussion of historical background, attention in this article goes to three major issues: the variation in synthesis associated with different academic genres; the kinds of insights into product and process that come from different research approaches; and the nature of new instructional approaches that emphasize elements of discourse synthesis. All facets of this research reveal continuity as well as change, the latter occurring, in large part, through contact and convergence of discourse synthesis research with related bodies of work. The conclusion, which centers on the notion of transformation, summarizes research conducted thus far and points to future directions.