Under the Age Discrimination in Employment Act, an employer may not discriminate against an employee who is over the age of forty because of that employee's age. That means that, in most circumstances, an employer may not treat an employee over the age of forty differently because of the employee's age with respect to the terms and conditions of employment, such as hiring, transfer, training, promotion, reassignment, or discharge. Age Discrimination in Employment Act does not require an employer to give special treatment to employees who are over the age of forty. Rather, the age of an employee is accorded neutral status under the Age Discrimination in Employment Act.

Employees may prove age discrimination by presenting direct evidence that their employer has discriminated against them because of age. An employee may also prove age discrimination by what is known as the McDonnell Douglas method of proof. Under this method, an employee may establish a prima facie case of age discrimination by proving different factors which depend upon the type of case involved (i.e., firing, demotion, reduction in force, refusal to train, failure to promote, etc.).