Most of the uninsured are either workers or family members of workers, and most Americans who are covered get their health insurance through the workplace. These facts motivate our study of two questions: Why do some workers have employer-sponsored health insurance while others do not? What policy initiatives are best suited to the specific conditions of most uninsured workers? We survey the literature on the working uninsured and use 1999 Current Population Survey data to paint a more detailed portrait of the working uninsured that can inform policy discussions.