The title of this special issue on diversity and international writing assessment signals both the complexity and potential of contemporary writing assessment. Writing assessment today is neither a narrow designed to sort writing samples neatly into categories nor the application of methods, even practice methods, without regard to their effects. Today, writing assessment is best understood as (1) designing a series of strategies to increase our knowledge of a complex construct — i.e., writing; (2) making meaningful decisions based on our measurement of that construct; and (3) understanding the effects of our practices on students and on ourselves. In short, writing assessment is about understanding the relationship between design, decisions, and effects. As such, diversity in contemporary writing assessment is neither about platitudes nor a priori binaries. Specifically, a diverse perspective on writing assessment means that researchers and teachers understand the effects of writing assessment on individual groups of students within specific contexts. In short, diversity in writing assessment research means paying attention to the consequences of writing assessment on all students’ learning and writing.