The ADA states that a "covered entity" shall not discriminate against "a qualified individual with a disability". This applies to job application procedures, hiring, advancement and discharge of employees, job training, and other terms, conditions, and privileges of employment. "Covered entities" include employers with 15 or more employees, as well as employment agencies, labor organizations, and joint labor-management committees. There are strict limitations on when a covered entity can ask job applicants or employees disability-related questions or require them to undergo medical examination, and all medical information must be kept confidential.
While the U.S. Department of Labor's (DOL) Office of Disability Employment Policy (ODEP) does not enforce the ADA, it does offer publications and other technical assistance on the basic requirements of the law, including covered employers’ obligation to provide reasonable accommodations to qualified job applicants and employees with disabilities. For a quick overview of the ADA read “The Americans with Disabilities Act: A Brief Overview.”
This past September marked the first time a judge ruled that the ADA applies even to businesses without a physical location. Scribd, an e-book subscription service is considered to provide "a place of public accommodation." Their services are not accessible to blind persons because they cannot be read with a screen reader. The judge reasoned, "Now that the Internet plays such a critical role in the personal and professional lives of Americans, excluding disabled persons from access to covered entities that use it as their principal means of reaching the public would defeat the purpose of this important civil rights legislation."
Once you have been hired and started work, your employer cannot require that you take a medical examination or ask questions about your disability unless they are related to your job and necessary for the conduct of your employer's business. Your employer may conduct voluntary medical examinations that are part of an employee health program, and may provide medical information required by State workers' compensation laws to the agencies that administer such laws.