According to the 2008 American Community Survey, about 12% of the population of the United States is living with one or more disabling conditions. These conditions impact lives in a variety of ways, some with more or less direct impact on an individual's health and access to health care services. Although it has been 20 years since the passage of the Americans with Disabilities Act, people with disabilities still experience health disparities and a lack of access to the appropriate care. This commentary is part of a collection of articles that describe various aspects of incorporating content into the medical school curriculum to enhance the preparation of today's medical students to meet the needs of people with disabilities. The authors briefly describe the scope of the problem and define the population of people with disabilities that constitutes the focus of the work described in the other articles in this collection.