This paper investigates trends in disability in the U.S. population, particularly among people under age fifty. Even as the elderly have become less disabled, reported disability has risen for younger Americans, especially those ages 30-49. We suggest some possible explanations for rising disability levels, such as obesity, technological advances in medicine, and changing disability insurance laws. Obesity and its attendant disorders seem particularly associated with these trends, although the data are not definitive. Whatever its sources, rising disability among the young could have adverse consequences for public programs such as disability insurance, Medicare, and Medicaid.