Health literacy is defined as the degree to which individuals can obtain, process, and understand basic health information and services needed to make appropriate health decisions. Based on the 2003 US National Assessment of Adult Literacy (NAAL), more than 90 million people have literacy levels rated as "basic" or "below basic." The Institute of Medicine recommends that health-related information be written at a sixth grade level or below. As Web-based health information is being accessed by more than 50 million people, a reading level assessment of the National Epilepsy Foundation of America Web site was undertaken. Two online programs were used to assess the reading level of each Web page in two main areas, "Understanding Epilepsy" and "Living with Epilepsy," using established readability formulas. One hundred seventy-six Web links were evaluated in English and 43 in Spanish. Based on the Flesch Reading Ease and Huerta Reading Ease assessments, 5.7% of National Epilepsy Foundation Web pages in English and 31-46% in Spanish had a sixth grade or lower reading level. Similar results have been reported in previous reviews of other health education Web sites in cancer, pediatrics, and asthma. The National Epilepsy Foundation Web site, a well-respected resource for patients and their families, contains a significant amount of health education content that is not appropriate for those with marginal health literacy. Editorial changes are needed to bring the information to suggested levels. Suggestions for developing appropriate materials are provided.