This special issue, comprised of five articles, examines the factors that contribute to writing proficiency and its development. The first discusses the proposition that the development of writing competence depends on high levels of self-regulation as well as a mastery of low level transcription skills. The second presents a developmental model which describes how multiple sources of knowledge, stored in long term memory, are coordinated during writing within the constraints of working memory. The third constructs a preliminary developmental model or writing and reading relationships which details the cognitive features that are critical to obtaining proficiency in both of these areas. In the fourth article, the conditions that contribute to the development of writing motivation are considered. The last paper examines how social/contextual variables influence writing and its development. Together, the articles provide substance and structure to some of the more important aspects of writing development.