The Age Discrimination in Employment Act of 1967 (ADEA) makes it illegal for an employer to discriminate against any employee or applicant for employment because the person is over the age of 40. Under the ADEA, all aspects of the employment relationship are implicated, including hiring, firing, promotion, layoff, benefits, job assignments, compensation, and training). The ADEA applies to all employers who have at least 20 or more employees, including state and local governments. It also applies to employment agencies and labor unions and organizations, as well as to the federal government.

It is also illegal under the ADEA for an employer to retaliate against an employee because he or she complained about practices that discriminate on the basis of age.

Age discrimination is sometimes subtle and employers attempt to hide discriminatory practices. Examples of age discrimination are the following:

• Requiring all workers to obtain a high school education or GED regardless of experience or job requirements.
• An employee is turned down for a position because he/she is "overqualified."
• Younger new employees are hired instead of promoting older employees with more experience with company.