Between 40 and 44 million persons in the United States have rudimentary literacy skills, and are unable to understand written materials that require only basic reading proficiency. The purpose of this report is to characterize the current status of illiteracy in the United States, describe the relationship between poor literacy and poor health, and make recommendations on how to deal with patients who have poor reading skills. Data collected by the National Work Group on Literacy and Health indicate that one quarter of the US population has rudimentary reading skills, and another 25% has limited reading skills. This makes it difficult to have written communication with much of the US population. Poor reading skills are associated with poor health and greater use of health services, but the basis for this association is unclear. Instruments are available to measure patients' reading skills in clinical settings, and information can be transmitted to patients in ways that make it understandable to poor readers. However, it is not known if using special low-literacy education materials with these patients improves health outcomes. When written communication with low-literacy patients is essential, materials should be at the 5th-grade level or lower, supplemented by nonwritten communication. Simple and nonwritten materials are appropriate for persons with limited literacy, and also for those with well-developed literacy. Research is needed to clarify the mechanisms through which illiteracy influences health status and health services utilization, and to determine if using low-literacy health education materials improves health outcomes.