More than an estimated 90 million adults in the United States lack the literacy skills needed for fully productive and secure lives. The effects of this shortfall are many: Adults with low literacy have lower rates of participation in the labor force and lower earnings when they do have jobs, for example. They are less able to understand and use health information. And they are less likely to read to their children, which may slow their children's own literacy development. At the request of the U.S. Department of Education, the National Research Council convened a committee of experts from many disciplines to synthesize research on literacy and learning in order to improve instruction for those served in adult education in the U.S. The committee's report, Improving Adult Literacy Instruction: Options for Practice and Research, recommends a program of research and innovation to gain a better understanding of adult literacy learners, improve instruction, and create the supports adults need for learning and achievement. "Improving Adult Literacy Instruction: Developing Reading and Writing," which is based on the report, presents an overview of what is known about how literacy develops the component skills of reading and writing, and the practices that are effective for developing them. It also describes principles of reading and writing instruction that can guide those who design and administer programs or courses to improve adult literacy skills. Although this is not intended as a "how to" manual for instructors, teachers may also find the information presented here to be helpful as they plan and deliver instruction.