This study reviews the current underlying theories relevant to writing centers as well as the research methods being used in the early 21st century. The first section covers the theories used in writing center scholarship from the 1980s onward based on influential articles and texts. The second section covers published research both in the Writing Center Journal (WCJ) and other publications from 2010 onward and discusses the current state of research methods. Readers may not be aware of some of the fine divisions of theory; for example, the distinction between collaborative learning and social constructivism. Researchers may benefit from the overview of methods, which covers the most popular and current methods (survey and textual analysis) and promising but little-published research methods, such as ethnography. Keywords : collaborative learning, social constructivism, writing as a social process, Zone of Proximal Development, scaffolding, cognitivism, feminism, transfer of learning, threshold concepts, tutoring encounter, social and environmental justice, survey, mixed methods, textual analysis, descriptive studies, theoretical research, archival research, quasi-experiment, quantitative methods, narrative inquiry, grounded theory, case study, usability, ethnography