To better understand what variables affect reader understanding of business writing, schema theory was compared to text-centered theory. Levels of readers' knowledge represented schema theory while message coherence represented textcentered theory. Newly developed instruments measured background knowledge and reader understanding. Text reading material was also developed. The research design consisted of a 2 x 2 factorial with business and nonbusiness subjects. The primary conclusion is that background knowledge (schema theory) affected a reader's ability to understand business communication. However, coherence (text-centered theory) did not affect understanding. Because coherence is only one textual quality, this study demonstrates the importance of additional research on the variables that affect reader understanding.What constitutes effective written business communication? Of V course, this is a global question that is difficult to answer. But many textbook writers implicitly answer the question when they provide prescriptions for business writing. A review of business communication textbooks indicates that most business writers consider the following qualities necessary for effective business writing: textbooks will combine several of these qualities into broader classifications, these specific qualities are addressed consistently. These qualities have been addressed in business communication textbooks for many years; however, their validity has been questioned. In a recent review of the history of business communication and the principles professed by business communication educators, Hagge (1989) said, Perhaps even more important, do the time-worn principles of business communication really have much validity? I would argue that the very uniformity of the principles I have shown to exist through a 2000-year-old epistolographic tradition suggests that they do not. In all the sources to which I have referred in this article, not once did I find any evidence that the authors who espoused the writing principles under investigation substantiated their pronouncements with any sort of empirically verifiable or philosophically defensible framework; instead, a number of times these principles were simply validated by reference to the rhetorical tradition that spawned them. (p. 48-49) at UQ Library on June 14, 2015 job.sagepub.com Downloaded from 8 In other words, the global question of what characteristics lead to effective business communication may have generally accepted answers, but these characteristics frequently have not been empirically tested. As a small step to empirically analyze what constitutes effective written business communication, we tested just two theoretical perspectives -schema theory and text-centered theoryon only one independent variable, reader understanding, in order to follow the rule of scientific reductionism. First, the reason is presented for selecting reader understanding as the dependent variable. Then the two competing theories are discussed.Reader Understanding Researchers, ei...