By the upper elementary grades, writing becomes an essential tool both for learning and for showing what you know. Students who struggle significantly with writing are at a terrible disadvantage. Data from the National Assessment of Educational Progress indicate that only 25% of students can be classified as competent writers; students with learning disabilities (LD) have even greater problems with writing than their normally achieving peers and frequently demonstrate a deteriorating attitude toward writing after the primary grades. In this article, we focus on composing and the writing process, and examine the knowledge base about writing development and instruction among students with LD. We address what research tells us about skilled writers and the development of writing knowledge, strategies, skill, and the will to write, and how this relates to students with LD. Next, we summarize what has been learned from research on writing development, effective instruction, and the writing abilities of students with LD in terms of effective instruction for these students. Finally, we indicate critical areas for future research.